Introduction - PETROL INJECTION SYSTEM

1.2 16v, 1.4 16v

GENERAL CHARACTERISTICS

The Bosch Motronic ME73H4 system (microhybrid control unit) with a motorized throttle belongs to the category of ignition systems integrated with sequential timed electronic injection system.

The fuel system is returnless.

The control unit electronically controls the air flow rate (flow meter) at the rotation speed set through the electronic butterfly, it regulates the fuel injection so that the (air/fuel) ratio is always within the optimum vlaues, calculating the moment of ignition, in order to allow the smooth operation of the engine as the environmental parameters and loads applied vary.

The ignition system is the static advance type with one coil with four outlets. The power modules are located inside the control unit.

The engine control system, which is the auto-adjusting type, is capable of recognizing the changes which take place in the engine and compensates for them according to auto-adjustment functions which correct the carburation and air flow rate plans stored in the control unit.

There are also two auto-adjustment functions for the carburation according to the anti-evaporation solenoid valve (see appropriate paragraph) and an idle adjustment plan: the latter is capable of effectively compensating for any air seepage.

The continuous auto-adjustment of the carburation makes it possible to have the correct quantity of fuel in all temperature and altitude conditions.

As a result of this, after each operation it is necessary to drive the vehicle for at leat 15 minutes in the various operating conditions, in order to ensure that the control unit memorizes any changes which have taken place in the system and end the adjustment.

The main operating principles of the system are basically as follows:

• regulation of injection times;
• adjustment of ignition advance values;
• control of cold starting;
• control of enrichment during acceleration
• fuel cut-off during deceleration
• management of the idle speed (also according to the battery voltage);
• limiting the maximum engine speed;
• control of combustion using the Lambda sensor;
• fuel vapour recovery;
• control of the electric fans;
• attachment/detachment of the climate control system;
• autodiagnosis.

There is also a special function that manages the connection with the body computer through a two-way signal for the Can line which includes:

• engine temperature for instrument panel (output);
• battery voltage (output);
• engine rpm (output) for instrument panel;
• max engine temperature warning light for instrument panel (output)
• engine oil pressure warning light for control panel (output);
• car speed (input) + mileometer (input);
• Fiat code anti-theft device (input/output);
• key status;
• fuel consumption meter signal (output) for trip computer
• fuel level gauge signal (input)

1.6 16v

The Marelli IAW 5NF system belongs to the category of systems integrated with:

• inductive discharge digital electronic ignition
• distributorless
• sequential, phased electronic injection (1-3-4-2).

1, Fuel tank

2, Electric fuel pump

3, Multi-purpose valve

4, Safety valve

5, Fuel delivery pipe

6, Injection-ignition ECU

7, Battery

8, Ignition switch

9, Inertia switch

10, Engine compartment junction unit

11, Climate control system

12, Fuel vapour cut-off valve

13, Injection timing sensor

14, Activated carbon filter

15, Body Computer (tester connection and Fiat CODE signal)

16, Absolute pressure and temperature sensor

17, Rpm and TDC sensor

18, Spark plugs

19, Coolant temperature sensor

20, Injectors

21, Throttle and throttle position sensor actuator

22, Accelerator pedal potentiometer

23, Fuel supply manifold

24, Air cleaner

25, Ignition coils

26, Lambda probe

27, System failure warning light

28, Rev counter

29, Catalytic converter

30, Lambda probe (post catalyzer)

1.8 16v

During idling, the control unit control the moment of ignition and the air flow rate to keep the engine running smoothly as the environmental parameters and the loads applied vary.

The control unit controls and manages the injection so that the air/fuel ratio is always sufficiently close to the stoichiometric value to maximize the conversion efficiency of the catalyzers.

The system's functions are basically as follows:

• self-adaption
• fault diagnosis
• Recognition of the CODE
• starting and post-starting;
• operation when cold;
• operation under full load conditions;
• operation in acceleration conditions;
• operation during over-run;
• operation in cut-off conditions
• – limiting the maximum engine speed;
• Operating with engine idling
• control of knock;
• Operation with variable valve timing active
• Control of the engine idle speed
• Control of the fuel vapour recovery
• control of modular manifold;
• control of radiator cooling fan;
• control of combustion
• recovery;
• diagnosis of Lambda sensors
• diagnosis of catalyzer
• misfire diagnosis;
• fuel system diagnosis

2.4 20v

Operation

The Bosch Motronic system belongs to the category of integrated systems:

• inductive discharge digital electronic ignition
• distributorless
• sequential phased electronic fuel injection (1 - 2 - 4 - 5 - 3).

The Engine Management Node controls:

• the air flow rate at the idle rotation speed set by the electronic throttle;
• the moment of ignition with the advantage of keeping the engine running smoothly as the ambient parameters and loads applied vary.

The Engine Management Node controls and manages the injection so that the air/fuel ratio is always sufficiently close to the stoichiometric value to maximize the conversion efficiency of the catalyzer; in full power and high usage conditions, the mixture is enriched to guarantee maximum performance.

The main operating principles of the system are basically as follows:

• self-learning;
• system self-adaptation;
• autodiagnosis;
• Recognition of the CODE
• control of cold starting;
• control of combustion - Lambda sensors;
• control of variable valve timing and modular inlet manifold
• control of knock;
• control of mixture enrichment during acceleration;
• fuel cut-off with the accelerator pedal released;
• fuel vapour recovery;
• control of the maximum rpm;
• control of fuel-electric fuel pump supply
• connection to the climate control system
• recognition of cylinder position;
• regulation of fuel injection times
• adjustment of ignition advance values
• control of the idle speed;
• control of engine cooling fans;
• connection with the automatic transmission control unit (where fitted);
• connection with ABS control unit;
• connection with the instrument panel;
• diagnosis of 'Fuel System'
• diagnosis of catalyzer
• diagnosis of Lambda sensors
• diagnosis of 'Misfire'

VIEW OF ASSEMBLY

1 - Electric fuel pump

2 - Relays

3 - Lambda sensor (upstream)

4 - Speedometer

5 - Rev counter

6 - Injection warning light

7 - Knock sensor

8 - Rpm sensor

9 - Fuel vapour recirculation solenoid valve

10 - Throttle body integral with D.V.E.

11 - Engine Management Node

12 - Modular inlet manifold solenoid valve

13 - Variable valve timing

14 - Injectors

15 - Climate control connector

16 - Diagnostic connector

17 - CODE connector

18 - Timing sensor

19 - Ignition coils

20 - Coolant temperature sensor

21 - Air flow meter with air temperature sensor

22 - Accelerator pedal potentiometer

23 - Brake pedal switch

24 - Clutch pedal switch

25 - Automatic transmission control unit (where fitted)

26 - Lambda sensor (downstream)

1.2 16v, 1.4 16v

Fuel injection system

The essential conditions that must always be met in the preparation of the air-fuel mixture for the correct operation of controlled-ignition engines are mainly:

• the 'metering' (air/fuel ratio) must constantly be kept as close as possible to the stoichiometric ratio, so as to ensure the necessary rapidity of combustion, avoiding unnecessary fuel consumption
• the 'homogeneity' of the mixture, consisting of petrol vapours, diffused as finely and evenly as possible in the air.

The injection/ignition system uses an indirect measuring system known as the 'SPEED DENSITY LAMBDA type.

In other words the angular rotation speed, density of the intake air and control of the mixture strength (retroactive control).

In practice the system uses data on the ENGINE SPEED (rpm) and AIR DENSITY (pressure and temperature) to measure the quantity of air drawn in by the engine.

The quantity of air drawn in by each cylinder, for each engine cycle depends not only on the density of the intake air, but also on the unit displacement and the volumetric efficiency.

The density of the air refers to that of the air drawn in by the engine and calculated according to the absolute pressure and the temperature, both detected in the inlet manifold.

Volumetric efficiency refers to the parameter relating to the coefficient for filling the cylinders measured on the basis of experimental tests carried out on the engine throughout the entire operating range and then stored in the electronic control unit memory.

Having established the quantity of intake air, the system has to provide the quantity of fuel according to the desired mixture strength.

The end of injection pulse or supply timing is contained in a map stored in the control unit memory and varies according to the engine speed and the pressure in the inlet manifold.

In practice, it involves processing which the electronic control unit carries out to command the sequential, phased opening of the four injectors, one per cylinder, for the length of time strictly necessary to form the air/petrol mixture which is closest to the stoichiometric ratio.

The fuel is injected directly into the manifold near the inlet valve at a pressure of around 3 bar.

The speed (number of revs per minute) and the density of the air (pressure and temperature) are used to measure the quantity of intake air which, when established, enables the quantity of fuel to be metered according to the desired mixture strength.

The other system sensors (coolant temperature, throttle valve position, battery voltage, etc.) allow the control unit to correct the basic strategy for all particular engine operating conditions.

It is vital for the air/fuel ratio to be around the stoichiometric value for the correct and prolonged operation of the catalytic silencer and for the reduction of pollutant emissions.

1.6 16v

During idling, the control unit checks:

• the ignition instant
• the air flow with the benefit of maintaining correct operation of the engine when the environmental parameters and applied loads vary.

The control unit controls and manages fuel injection so that the stoichiometric ratio (air/fuel) is always at the optimum value.

The system's functions are basically as follows:

• system self-adaptation
• self test
• recognition of FIAT CODE
• control of cold starting
• control of combustion - Lambda sensors
• control of detonation
• control of mixture enrichment during acceleration
• fuel cut-off during overrunning
• fuel vapour recovery
• limitation of the maximum rpm
• fuel pump control
• connection to the climate control system
• recognition of cylinder position
• adjustment of injection times
• adjustment of ignition advance values
• control and management of the idle speed
• control of electric cooling fan.

1.8 16v

The diagram below illustrates the main system components.

1, Electric fuel pump

2, Inertia switch

3, Speedometer

4, Battery

5, Ignition switch

6, Injection system relays

7, Air conditioning compressor

8, Injection/ignition control unit

9, Rev counter

10, Diagnostic socket

11, System failure warning light

12, Butterfly position sensor

13, Motorized throttle casing with air flow meter incorporated

14, Engine idle adjustment actuator

15, Modular manifold actuator solenoid valve

16, Phase transformer electro-magnet

17, Injectors

18, Ignition coil

19, Cam angle sensor

20, Radiator fan

21, Rpm sensor

22, Detonation sensor

23, Engine coolant temperature sensor

24, Fuel vapour recovery solenoid valve

25, Lambda sensor upstream of catalyzer

26, Body computer (with Fiat CODE function)

26, Lambda sensor downstream of catalyzer

2.4 20v

Operation

Diagram showing information entering/leaving ENGINE MANAGEMENT NODE

1 - Electric fuel pump

2 - Air conditioner compressor

3 - Electric fan

4 - Lambda sensor downstream of catalyzer

5 - Quadrinary

6 - Brake pedal switch

7 - Timing sensor

8 - Speedometer

9 - Pre-catalyzer upstream Lambda sensor

10 - Coolant temperature sensor

11 - Detonation sensor (two)

12 - Rpm sensor

13 - Accelerator pedal potentiometer

14 - Air flow meter with air temperature sensor

15 - Battery

16 - Clutch pedal switch

17 - Throttle casing integrated with D.V.E.

18 - CAN line (for communication with ABS/ASR control units)

19 - Lancia CODE

20 - Diagnostic socket

21 - Fuel vapour recirculation solenoid

22 - Ignition coils

23 - Injection warning light

24 - Modular intake manifold solenoid valve

25 - Rev counter

26 - Variable valve timing

27 - Injectors

1.2 16v, 1.4 16v

Ignition system

The ignition is of the inductive discharge type, breakerless with power modules located in the electronic injection/ignition control unit.

The primary winding for each coil is connected to the power relay (thereby receiving the battery voltage) and to the pins for the electronic control unit for connection to earth.

After the starting stage, the electronic unit manages the basic advance taken from a special map according to the:

• engine rpm
• absolute pressure value (mmHg) measured in the inlet manifold.

This advance value is corrected according to the temperature of the engine coolant and the intake air.

The cylinder spark plugs are connected directly to the coil secondary terminals (one per spark plug).

1.6 16v

Fuel injection system

The essential conditions that must always be met in the preparation of the air-fuel mixture for the correct operation of controlled-ignition engines are mainly:

• the 'metering' (air/fuel ratio) must constantly be kept as close as possible to the stoichiometric ratio, so as to ensure the necessary rapidity of combustion, avoiding unnecessary fuel consumption
• the 'homogeneity' of the mixture, consisting of petrol vapours, diffused as finely and evenly as possible in the air.

The injection/ignition system uses an indirect measuring system known as the 'SPEED DENSITY LAMBDA type. in other words the angular rotation speed, density of the intake air and control of the mixture strength.

In practice the system uses data on the ENGINE SPEED (rpm) and AIR DENSITY (pressure and temperature) to measure the quantity of air drawn in by the engine.

The quantity of air drawn in by each cylinder, for each engine cycle depends not only on the density of the intake air, but also on the unit displacement and the volumetric efficiency.

The density of the air refers to that of the air drawn in by the engine and calculated according to the absolute pressure and the temperature, both detected in the inlet manifold.

Volumetric efficiency refers to the parameter relating to the coefficient for filling the cylinders measured on the basis of experimental tests carried out on the engine throughout the entire operating range and then stored in the electronic control unit memory.

Having established the quantity of intake air, the system has to provide the quantity of fuel according to the desired mixture strength.

The end of injection pulse or supply timing is contained in a map stored in the control unit memory and varies according to the engine speed and the pressure in the inlet manifold. In practice, it involves processing which the electronic control unit carries out to command the sequential, phased opening of the four injectors, one per cylinder, for the length of time strictly necessary to form the air/petrol mixture which is closest to the stoichiometric ratio.

The fuel is injected directly into the manifold near the inlet valve at a pressure of around 3.5 bar.

Whilst the speed (rpm) and the density of the air (pressure and temperature) are used to measure the quantity of intake air, which when established allows the quantity of fuel to be metered according to the desired mixture strength, the other sensors in the system (coolant temperature, butterfly valve position, battery voltage, etc.) allow the electronic control unit to correct the basic strategy for all engine operating conditions.

It is vital for the air/fuel ratio to be around the stoichiometric value for the correct and prolonged operation of the catalytic silencer and for the reduction of pollutant emissions.

1.8 16v

INJECTION SYSTEM

Injection control strategies are designed to supply the engine with the correct amount of fuel to meet engine service needs at the required moment.

The presence of the air flow meter makes it possible to directly measure the mass of intake air making the presence of the intake air temperature sensor superfluous.

The injection management strategies basically consist of calculating the injection time, determining the injection phase and then implementing them by operating the injectors.

The base pulse constant depends on injector characteristics and corresponds to the quantity of fuel injected into each cylinder.

According to the throttle opening, fuel quantity is computed, in turn, by dividing the quantity of air taken in by each cylinder by the required mixture concentration for each engine service point.

Final injection time is calculated by using a calculating algorithm whereby base pulse constant is corrected by a set of coefficients that take into account the different engine operating conditions, as revealed by system sensors.

A, Base pulse constant

B, Corrective factors (low engine temperature, high engine temperature, starting and post-starting, full throttle opening, deceleration, acceleration)

C, Retroactive mixture control

D, Self-adaption

E, Cut-off

F, Intermediate injection time

G, Extra pulse

H, Non-phased injection control

2.4 20v

INTRODUCTION

Fuel injection system

The essential conditions that must always be met in the preparation of the air-fuel mixture for the correct operation of controlled-ignition engines are mainly:

• the 'metering' (air/fuel ratio) should constantly be kept as close as possible to the stoichiometric ratio, so as to ensure the maximum conversion capacity for the catalytic converter (max. efficiency).
• the 'homogeneity' of the mixture, consisting of petrol, diffused as finely and evenly as possible in the air.

The information processed by the Engine Management Node for controlling optimum metering is received in the form of electrical signals emitted by:

• air flow meter and air temperature sensor, for the exact quantity of air drawn in
• rpm sensor which produces an alternating, single-phase signal whose frequency indicates the engine rpm. This signal is used by the Engine Management Node for detecting misfire
• throttle potentiometer, to recognize the acceleration conditions requested
• coolant temperature sensor located on the thermostat
• Lambda sensors to determine the oxygen content of the exhaust gases and, through the downstream sensor, to diagnose the efficiency of the catalyzers.

Ignition system

The ignition system is the inductive discharge static advance type, (i.e. without a High Tension distributor) with power modules located inside the Engine Management Node.

In the ignition system each coil supplies the spark plugs for the appropriate cylinder.

The advantages of this solution are:

• less electrical overload;
• guarantee of constant discharge at each spark plug.

Stored in the Engine Management Node, there is a map containing the entire set of optimum ignition advance values (for the cylinder at the power stroke) that the engine can adopt in relation to the rpm and required engine load.

The Engine Management Node corrects the advance values mainly in accordance with:

• engine coolant temperature
• intake air temperature
• knock
• throttle valve position

The information which the Engine Management Node processes to operate the ignition coils is received by means of electrical signals emitted by the:

• air flow meter and air temperature sensor, for the exact quantity of air drawn in
• rpm sensor, which generates an alternating single-phase signal whose frequency indicates the engine rpm
• 2 knock sensors (on the rear of the cylinder block/crankcase, one between the 1st and 2nd cylinders, the other between the 4th and 5th cylinders) to recognize which cylinder is knocking and correct the ignition advance
• throttle position potentiometer, to recognize minimum, partial opening and full load conditions
• timing sensor.

1.2 16v, 1.4 16v

Diagram of input/output info to/from control unit

The diagram below shows the information entering/leaving the control unit.

1, Engine control unit

2, Battery

3, Ignition

4, Engine control system relay

5, Fuel pump relay

6, Fuel pump

7, Radiator fan relay/s

8, Radiator fan

9, Compressor activation relay

10, Compressor

11, Ignition coils

12, Spark plugs

13, Injectors

14, Carbon filter flushing solenoid

15, Lambda sensor (pre-catalyzer)

16, Lambda sensor (post-catalyzer)

17, Coolant temperature sensor

18, Detonation sensor

19, Throttle and throttle position sensor control actuator

20, Engine rpm and TDC sensor

21, Injection timing sensor

22, Air temperature and absolute pressure sensor

23, Oil pressure switch

24, Body computer

25, CODE control unit (via CAN)

26, Tester connection (via CAN network)

27, Rev counter (via CAN network)

28, System failure bulb (via CAN)

29, Speedometer (via CAN)

30, City button for power assisted steering (via CAN)

1.6 16v

Ignition system

The ignition is of the inductive discharge type, breakerless with power modules located in the electronic injection/ignition control unit.

The system has a coil for each cylinder connected directly to the spark plug.

The primary winding for each coil is connected to the power relay (thereby receiving the battery voltage) and to the pins for the electronic control unit for connection to earth.

After the starting stage, the electronic unit manages the basic advance taken from a special map according to the:

• engine rpm
• absolute pressure value (mbar) measured in the inlet manifold.

This advance value is corrected according to the temperature of the engine coolant and the intake air.

1.8 16v

IGNITION SYSTEM

Ignition control strategies are designed to trigger a spark with the required advance according to engine service condtions

Ignition management essentially involves calculating the ignition advance and then implementing ignition by controlling a power transistor built into each coil.

The base pulse constant computed on the basis of intake air flow and engine speed is corrected to allow for different engine service conditions.

The control unit determines the instant at which the coil primary winding begins to conduct current on the basis of engine rpm.

This instant naturally changes in relation to the angular distance from exhaust TDC in each cylinder: the advance is directly proportional to engine rpm provided the time required (dwell) to saturate the coil primary winding with current is more or less constant.

The moment conduction begins is corrected according to battery voltage.

1, System supply relay

2, Interface connector

3, Individual ignition coil (pencil coil)

2.4 20v

Self-learning

The Engine Management Node implements the self-learning logic in the following conditions:

removing-refitting or replacing the Engine Management Node

removing, refitting or replacing the butterfly casing.

The values memorized by the Engine Management Node are preserved if the battery is disconnected.

1.2 16v, 1.4 16v

SELF-LEARNING

The control unit implements the self-learning logic in the following conditions: *-removing/refitting or replacing injection contro lunit* - removing/refitting or replacing throttle casing

The values memorized by the control unit are preserved if the battery is disconnected.

1.6 16v

Diagram of input/output info to/from control unit

The fuel level and engine oil presssure data reach the control unit via the CAN line.

1, Engine control unit

2, Battery

3, Ignition

4, Engine control system relay

5, Fuel pump relay

6, Fuel pump

7, Radiator fan relay/s

8, Radiator fan

9, Compressor activation relay

10, Compressor

11, Injectors

12, Spark plugs

13, Ignition coils

14, Carbon filter flushing solenoid

15, Lambda sensors (pre-catalyzer and post-catalyzer)

16, Coolant temperature sensor

17, Knock sensor

18, Throttle and throttle position sensor actuator

19, Engine rpm and TDC sensor

20, Air pressure and absolute temperature sensor

21, Engine oil pressure switch

22, Body computer

23, CODE control unit (body computer) (via CAN)

24, Tester connection (via CAN line)

25, Rev counter (via CAN line)

26, System failure bulb (via CAN line)

27, Speedometer (via CAN line)

28, Injection timing sensor

29, Accelerator pedal sensor

30, Clutch pedal switch

31, Coolant temperature sensor

1.8 16v

DIAGRAM OF INPUT/OUTPUT INFORMATION TO/FROM THE CONTROL UNIT

The diagram below shows the main information entering/leaving the control unit.

1, Engine control unit

2, Battery

3, Ignition

4, System supply relay

5, Electric fuel pump

6, Climate control system

7, Radiator fan relay

8, Radiator fan

9, Body Computer (with Fiat CODE function)

10, Timing variator solenoid relay

11, Timing variator solenoid

12, Rev counter

13, Lambda sensor upstream of catalyzer

14, Tester connection

15, Ignition coils

16, Injectors

17, Fuel vapour solenoid

18, Modular manifold actuator control solenoid

19, Lambda sensor downstream of catalyzer

20, Coolant temperature sensor

21, Speedometer

22, Accelerator pedal potentiometer

23, Knock sensor

24, Cam angle sensor

25, Engine rpm sensor

26, Motorized throttle body with air flow meter incorporated

27, Fuel pump relay

2.4 20v

System self-adaptation

The Engine Management Node has a self-adaption function which recognizes changes in the engine which occur as a result of bedding-in and ageing processes of both components and the engine itself.

These changes are stored in the form of modifications to the basic mapping, and their purpose is to adapt the operation of the system to the gradual alterations in the engine and components compared with their characteristics when new.

This self-adaptation function also makes it possible to even out inevitable differences (due to production tolerances) in any replaced components.

From the exhaust gas analysis, the Engine Management Node changes the basic mapping in relation to the original characteristics of the new engine.

The self-adaptation parameters are not cancelled if the battery is disconnected.

1.2 16v, 1.4 16v

SELF-ADAPTATION OF THE SYSTEM

The control unit has a self-adaption function which recognizes changes in the engine which occur as a result of bedding-in and ageing processes of both components and the engine itself.

These changes are stored in the form of modifications to the basic mapping, and their purpose is to adapt the operation of the system to the gradual alterations in the engine and components compared with their characteristics when new.

This self-adaptation function also makes it possible to even out inevitable differences (due to production tolerances) in any replaced components.

From the exhaust gas analysis, the control unit changes the basic mapping in relation to the original characteristics of the new engine.

The self-adaptation parameters are not cancelled if the battery is disconnected.

1.6 16v

System self-adaptation

The control unit has a self-adaption function which recognizes changes in the engine which occur as a result of bedding-in and ageing processes of both components and the engine itself.

These changes are stored in the form of modifications to the basic mapping, and their purpose is to adapt the operation of the system to the gradual alterations in the engine and components compared with their characteristics when new.

This self-adaptation function also makes it possible to even out inevitable differences (due to production tolerances) in any replaced components.

From the exhaust gas analysis, the control unit changes the basic mapping in relation to the original characteristics of the new engine.

The self-adaptation parameters are not cancelled if the battery is disconnected.

1.8 16v

SELF-ADAPTATION

The control unit has a self-adaptation function which stores deviations between base mapping and corrections imposed by the lambda probe that recur persistently during operation.

These deviations (due to system and engine component ageing) are stored permanently to allow the system to adapt to gradual changes in the engine and its components in relation to original specifications.

This strategy is disabled whilst the charcoal filter solenoid valve is open.

If the control unit is changed, a road test should be carried out to allow the engine to warm up and the control unit (particularly while idling at a standstill) to implement self-adaption.

2.4 20v

Self-diagnosis

The Engine Management Node autodiagnostic system controls the correct operation of the system and signals any faults by means of an (MIL) warning light in the instrument panel which has a standardized European colour and ideogram. This warning light signals both engine management faults and problems detected by the EOBD strategies.

The (MIL) warning light operating logic is as follows:

• with the ignition key in the ON position, the warning light comes on and remains on until the engine has been started up. The Engine Management Node self-test system checks the signals coming from the sensors, comparing them with the permitted limits:

Signalling of faults during engine starting:

• the failure of the warning light to go out after the engine has been started up means that there is an error memorized in the Engine Management Node.

Fault indication during operation

• the warning light flashing indicates possible damage to the catalyzer due to misfire.
• the warning light on constantly indicates the presence of engine management errors or EOBD errors.

RECOVERY

From time to time the Engine Management Node defines the type of recovery according to the faulty components. The recovery parameters are managed by those components which are not faulty.

1.2 16v, 1.4 16v

AUTODIANOSIS AND RECOVERY

The control unit autodiagnostic system controls the correct operation of the system and signals any faults by means of an (MIL) warning light in the instrument panel which has a standardized European colour and ideogram.

This warning light signals both engine management faults and problems detected by the EOBD strategies.

The (MIL) warning light operating logic is as follows:

With the ignition key in the ON position, the warning light comes on and remains on until the engine has been started up. The control unit's self-test system checks the signals coming from the sensors, comparing them with the permitted limits:

Signalling of faults during engine starting:

• the failure of the warning light to go out once the engine has been started up means that there is an error memorized in the control unit.

Fault indication during operation

• the warning light flashing indicates possible damage to the catalyzer due to misfire.
• the warning light on constantly indicates the presence of engine management errors or EOBD errors.

From time to time, the control unit defines the type of recovery according to the components which are faulty.

The recovery parameters are managed by those components which are not faulty.

1.6 16v

Self-diagnosis

The control unit autodiagnostic system controls the correct operation of the system and signals any faults by means of an (MIL) warning light in the instrument panel which has a standardized European colour and ideogram.

This warning light signals both engine management faults and problems detected by the EOBD strategies.

The (MIL) warning light operating logic is as follows:

• with the ignition key in the ON position, the warning light comes on and remains on until the engine has been started up.
• The control unit's self-test system checks the signals coming from the sensors, comparing them with the permitted limits.

Signalling of faults during engine starting:

• the failure of the warning light to go out once the engine has been started up means that there is an error memorized in the control unit.

Fault indication during operation

• the warning light flashing indicates possible damage to the catalyzer due to misfire.
• if the warning light comes on fixed, it indicates the presence of engine management errors or EOBD RECOVERY diagnosis errors

From time to time, the control unit defines the type of recovery according to the components which are faulty.

The recovery parameters are managed by those components which are not faulty.

1.8 16v

DIAGNOSTICS

The system has an autodiagnostic function which checks for any irregularities in the components listed below.

Actuators:

• Injectors
• Coils
• Fuel vapour solenoid
• Motorized throttle actuator
• Electric fuel pump relay
• Modular manifold solenoid valve
• Phase transformer solenoid valve relay
• Climate control compressor relay (if fitted)

Sensors:

• Engine rpm sensor
• Cam angle sensor
• Air flow meter
• Lambda sensors (upstream/downstream)
• Coolant temperature sensor
• Detonation sensor
• Throttle position sensor

If a fault is confirmed, it is stored permanently and the relevant sensor is cut out of the system until it can be reset.

The control unit autodiagnostic system controls the correct operation of the system and signals any faults by means of an (MIL) warning light in the instrument panel which has a standardized European colour and ideogram.

This warning light signals both engine management faults and problems detected by the EOBD strategies.

The (MIL) warning light operating logic is as follows:

• with the ignition key in the ON position, the warning light comes on and remains on until the engine has been started up. The control unit's self-test checks the signals coming from the sensors, comparing them with the permitted limits:
• the failure of the warning light to go out once the engine has been started up means that there is an error memorized in the control unit.
• the warning light flashing indicates possible damage to the catalyzer due to misfire.
• the warning light on constantly indicates the presence of engine management errors or EOBD errors.

2.4 20v

Recognition of the CODE

The moment the Body Computer receives the ignition ON signal, it converses with the Engine Management Node to allow starting. For vehicles equipped with Passive Entry see [DF55].

1.2 16v, 1.4 16v

RECOGNITION OF FIAT CODE

When the control unit receives the ignition 'ON signal, it communicates with the body computer to obtain starting enablement.

Communication takes place via a two-way CAN line which connects the two control units.

1.6 16v

Recognition of FIAT CODE

When the control unit receives the ignition 'ON signal, it dialogues with the Body Computer (Fiat CODE function) to obtain starting enablement.

Communication takes place via the CAN line which connects the two control units.

1.8 16v

RECOVERY

If a fault is detected in the sensors/actuators, the control unit software reconstructs and replaces the missing information if possible so that the engine can continue to operate.

Not all engine management errors cause the warning light to come on.

The system can be fully tested using a tester. This takes place in three stages:

• Displaying a series of functional parameters (with the engine switched off or running)
• Displaying the errors and deleting them
• Activating some of the actuators (active diagnosis).

2.4 20v

Control of cold starting

The following occurs during cold starting:

• the mixture naturally becomes leaner and evaporation is thus lower (poor fuel particle turbulence at low temperatures)
• reduced fuel evaporation
• condensation of the fuel on the inner walls of the inlet manifold
• increased viscosity of the lubricant oil.

The Engine Management Node recognizes this condition and corrects the fuel injection times in accordance with:

• coolant temperature
• intake air temperature
• battery voltage
• engine rpm.

The ignition advance depends solely on the engine rpm and the coolant temperature.

Whilst the engine is warming up, the Engine Management Node operates the motorized butterfly to regulate the quantity of air required to ensure that the engine does not cut out.

The rpm is made to decrease in proportion to the increase in temperature of the engine until the optimum value with the engine up to temperature is obtained.

1.2 16v, 1.4 16v

CONTROL OF COLD STARTING

The following occurs during cold starting:

• a natural weakening of the mixture because of poor turbulence of the fuel particles at low temperatures
• reduced fuel evaporation
• condensation of the fuel on the inner walls of the inlet manifold
• increased viscosity of the lubricant oil.

The electronic control unit recognizes this condition and corrects the fuel injection time in accordance with:

• coolant temperature
• intake air temperature
• battery voltage
• engine rpm.

The ignition advance depends solely on the engine rpm and the coolant temperature.

The rpm is made to decrease in proportion to the increase in temperature of the engine until the optimum value with the engine up to temperature is obtained.

1.6 16v

RECOGNITION OF CYLINDER POSITION

The engine timing signal, together with the engine rpm and top dead centre (TDC) signal, allows the control unit to recognize the succession of cylinders to implement phased injection.

This signal is generated by a Hall-effect sensor, positioned on the rocker cover near the phonic wheel formed on the camshaft pulley.

1.8 16v

CODE RECOGNITION

When the control unit receives the ignition 'ON signal, it converses with the Body Computer (Fiat CODE function) and, if the correct code has been received, gives a go ahead for starting.

Communication takes place via the dedicated bidirectional serial line which connects the two control units.

2.4 20v

Check on combustion - Lambda probe

In EOBD systems the Lambda sensors, which are all the same type, are located upstream of the catalyzer and downstream of the catalyzer. The upstream sensors carry out the check on the mixture strength known as the 1st loop (upstream sensor closed loop). The sensor downstream of the catalyzer is used for the catalyzer diagnosis and for finely modulating the 1st loop control parameters. With this in mind, the adjustment of the second loop is designed to recover both production differences and those in the response of the upstream sensors which may occur as a result of ageing and pollution. This control is known as the 2nd loop (downstream sensor closed loop).

1.2 16v, 1.4 16v

CONTROL OF COMBUSTION - LAMBDA SENSORS

In EOBD systems the Lambda sensors, which are all the same type, are located upstream of the catalyzer and downstream of the catalyzer.

The pre-catalyzer sensor carries out the check on the mixture strength called 1st loop (closed loop of the upstream sensor).

The post-catalyzer sensor is used for the catalyzer diagnosis and for finely modulating the 1st loop control parameters.

With this in mind, the adjustment of the second loop is designed to recover both production differences and those in the response of the pre-catalyzer sensors which may occur as a result of ageing and pollution.

This control is known as the 2nd loop (post-catalyzer sensor closed loop).

1.6 16v

CONTROL OF COMBUSTION - LAMBDA SENSORS

In EOBD systems the Lambda sensors, which are all the same type but not interchangeable, are located one before (pre-) the catalyzer and one after (post-) the catalyzer.

The pre-catalyzer sensor carries out the check on the mixture strength called 1st loop (closed loop of the pre-catalyzer sensor).

The post catalyzer sensor is used for the catalyzer diagnosis and for finely modulating the 1st loop control parameters.

With this in mind, the adjustment of the second loop is designed to recover both production differences and the slight deviations which the response from the pre-catalyzer sensor may show as a result of ageing and pollution.

This check is called 2nd loop control (closed loop of post-catalyzer sensor).

1.8 16v

INJECTION MANAGEMENT

Base pulse constant is increased by a multiplication coefficient for the entire time the engine is driven by the starter motor.

After starting, the coefficient is gradually reduced until it disappears within a certain period; the lower the engine temperature, the longer this period.

The control unit immediately recognises the engine timing setting upon start-up It is therefore able to manage the phased injection from the first combustion

k, Enrichment factor

t, Time

a, Engine temperature function decrease

ON, Engine cranked

OFF, Engine running

2.4 20v

Check on timing variator and modular inlet manifold

To optimize the quantity of air drawn in by the engine, the Engine Management Node checks:

• inlet timing at two angular positions;
• geometry of inlet ducts over two lengths.

At the maximum torque speed, the Engine Management Node sets the 'open' phase:

• cam advanced by 18° engine
• inlet box long ducts

At the maximum power speed and during idling, the Engine Management Node sets the 'closed' phase:

• cam in normal position
• inlet box short ducts.

In the other engine operating conditions, the Engine Management Node selects the most suitable configuration to optimize performance, consumption and emissions.

During overrunning, the inlet ducts of the box are always short.

1.2 16v, 1.4 16v

CONTROL OF DETONATION

The control unit detects the presence of knocking by processing the signal coming from the relevant sensor.

The control unit continuously compares the signals coming from the sensor with a threshold value, which, in turn, is continuously updated to take account of background noise and ageing of the engine.

The control unit is therefore capable of detecting the presence of detonation (or the onset of detonation) in each individual cylinder and reduces the ignition advance for the cylinder concerned (in steps of 3 degrees up to a maximum of 6 degrees) until the phenomenon disappears. The advance is then gradually restored to the basic value (in steps of 0.8 degrees).

Under acceleration conditions, a higher threshold is used to take account of the increased engine noise under such conditions.

The knock control strategy also has a self-adaptation function, which memorizes the reductions in advance that may be repeated continuously, so as to adjust the mapping to the different conditions now affecting the engine.

1.6 16v

Operation when cold

Under these circumstances there is a natural weakening of the mixture because of the poor turbulence of the fuel particles at low temperatures, reduced evaporation and condensation on the inner walls of the inlet manifold, all of which is exacerbated by the increased viscosity of the lubricant oil which, as is well known, increases the rolling torque of the engine mechanical components at low temperatures.

The electronic control unit recognizes this condition on the basis of the coolant temperature signal, increasing the basic injection time.

1.8 16v

IGNITION MANAGEMENT

Upon start-up, advance cannot be controlled as normal because considerable fluctuations in speed of rotation mean that advance cannot be correctly computed.

The advance is therefore managed by taking the tooth at 65 as a reference for the start of conduction and the tooth at 10 for the ignition advance.

As a result there is a fixed advance of 10° for the entire time the engine is driven by the starter motor.

2.4 20v

Check on knocking

The Engine Management Node detects the presence of knocking by processing the signal coming from the relevant sensors.

The Engine Management Node continuously compares the signals coming from the sensors with a threshold value, which, in turn, is continuously updated to take account of background noise and ageing of the engine.

The Engine Management Node is therefore capable of detecting the presence of detonation (or the onset of detonation) in each individual cylinder and reduces the ignition advance for the cylinder concerned (in steps of 3 degrees up to a maximum of 6 degrees) until the phenomenon disappears. The advance is then gradually restored to the basic value (in steps of 0.8 degrees).

Under acceleration conditions, a higher threshold is used to take account of the increased engine noise under such conditions.

The knock control strategy also has a self-adaptation function, which memorizes the reductions in advance that may be repeated continuously, so as to adjust the mapping to the different conditions now affecting the engine.

1.2 16v, 1.4 16v

CONTROL OF ENRICHMENT DURING ACCELERATION

During this stage, the control unit increases the quantity of fuel requested by the engine as appropriate (to achieve maximum torque) according to the signals coming from the following components:

• throttle potentiometer;
• Rpm and TDC sensor

The 'basic' injection time is multiplied by a coefficient which depends on the temperature of the engine coolant, the opening speed of the accelerator butterfly and the increase in pressure in the inlet manifold.

If the sharp variation in the injection time is calculated when the injector is already closed, the control unit reopens the injector (extra pulse) in order to compensate the mixture strength extremely quickly; the subsequent injections are already increased on the basis of the coefficients mentioned previously.

1.6 16v

Operation under full load

Operation in full load conditions is detected, by the control unit, through the values supplied by the butterfly position and absolute pressure sensors.

In full load conditions, the basic injection time must be increased to obtain the maximum power supplied by the engine.

1.8 16v

ADJUSTMENT OF THE LAMBDA VALUE

An effective way of reducing the harmful emissions in the exhaust gases is the post-treatment of the exhaust gases in the three-way catalyzer. This converts the three harmful components in the exhaust gases CO, HC and NOX into H20, CO2 and N2.

Conversion of all three components can only be achieved if the mixture ratio is kept sufficiently close to a stoichiometric level.

The 'lambda' factor is normally used instead of mixture ratio to indicate the ratio between the current mixture ratio and the stoichiometric ratio

If 'lambda' is equal to 1, the engine is supplied with a stochiometric mixture. If 'lambda' is greater than 1, the mixture is lean. If 'lambda' is less than 1, the mixture is rich.

To achieve optimum service conditions, the control unit works retroactively or in a closed loop based on signals from the lambda sensor.

When the sensor signal indicates a rich mixture, the control unit reduces the supply to the injectors. When the signal indicates a lean mixture, it increases the supply to the injectors.

The system therefore comprises the engine (controlled system), the Lambda sensor (measuring element), the control unit (regulator) and the injectors (actuators).

2.4 20v

Check on enrichment during acceleration

If during the acceleration demand, the variation in the air flow meter signal exceeds a predefined increment, the Engine Management Node increases the fuel injection time so that the required rpm is reached rapidly.

Recovery:

The Engine Management Node replaces the signal coming from the faulty air flow meter with an air flow signal calculated on the basis of engine rpm and throttle position.

1.2 16v, 1.4 16v

CONTROLLING FUEL SUPPLY - FUEL PUMP

The control unit supplies the electric pump:

• when the ignition is ON for 0.8 s
• with the ignition in the START position and the engine speed > 22.8 rpm

The control unit cuts off the supply to the electric pump:

• with ignition in OFF position
• with engine speed < 22.8 rpm.

The returnless fuel supply system ensures a constant petrol pressure of 3.5 bar.

1.6 16v

Operation during over-run

During this stage the engine has two strategies:

• A negative, transitory strategy to keep the quantity of fuel supplied to the engine at the stoichiometric value (less pollution). This stage is recognized by the control unit when the butterfly position signal goes from a high voltage reading to a lower one.
• A soft accompaniment strategy at the lower speed (dash-pot) to lessen the variation in the torque supplied (reduced engine braking).

1.8 16v

LAMBDA SYSTEM OPERATION

The control unit changes the injection time by means of a PID (proportional, integrated, derivative) regulator, thus allowing the lambda sensor to generate a tovoltage signal which varies from 50 mV (lean) to 900 mV (rich).

Following the Lambda sensor output signal, the control unit modifies the injection time, by mean of the regulator, thereby allowing the engine to operate within the optimum factor for the conversion of the gases in the catalyzer (target).

2.4 20v

Fuel cut-off during over-run

During release of the accelerator pedal, and beyond a pre-established threshold, the Engine Management Node:

• cuts off the supply to the fuel injectors
• reactivates fuel supply to the injectors at 1200-3000 rpm(the threshold depends on engine temperature and speed engaged).

As there is no fuel supply, the rpm decreases more or less rapidly depending on the vehicle's driving conditions.

Before idle speed is reached, the trend of the fall in rpm is checked.

If it exceeds a certain value, the fuel supply is partially reactivated so that the engine can 'gently accompany' the drop towards idle speed.

The thresholds for reactivation of the fuel supply and for fuel cut-off vary depending on:

• engine coolant temperature
• vehicle speed
• engine rpm

1.2 16v, 1.4 16v

CONNECTION WITH THE CLIMATE CONTROL SYSTEM

When the compressor turns on and power is required, the control unit drives the motorized throttle to increase the air flow.

The control unit momentarily interrupts the supply to the compressor:

• during starting
• by switching it off over 6200 rpm
• by switching it off if the engine temperature > 112°C.
• during pick-up with accelerator fully depressed.

1.6 16v

Barometric correction

Atmospheric pressure varies according to the altitude creating a variation in the volumetric efficiency which requires correction of the basic mixture strength (injection time).

The correction of the injection time depends on the variation in altitude and is automatically updated by the electronic control unit each time the engine is switched off and in certain butterfly position and rpm conditions. (for example at low speeds and with the butterfly wide open)

1.8 16v

CORRECTION FUNCTION AND SELF-ADAPTATION

The components in the engine and the injection system can undergo variations, in relation to the optimum conditions, due to ageing or momentary malfunctions.

The Lambda system is capable of correcting these variations using the correction and autoadjustment functions.

Following a non optimum Lambda sensor signal response as a result of a malfunction of a general nature, the control unit implements a correction of more or less 21% of the mixture strength.

If the correction factor persists, the control unit adjusts its map on the basis of the new engine conditions. The self-adaptation, like the correction factor, can reach a maximum level of 21%.

The vehicle exhaust system uses the following:

• two Lambda sensors at the outlet of the exhaust manifold and before the pre-catalyzers which control the closed loop combustion of the pairs of cylinders 1-4 and 2-3.
• a third Lambda sensor, positioned after the third catalyzer, which has the task of diagnosing the main overall conversion efficiency.

2.4 20v

Fuel vapour recovery

The vapours developed by the petrol in the tank are colleced in a decanter, which condenses them as far as possible and directs them to the tank through suitable ducts.

The reamining vapours are absorbed by a charcoal filter (canister) from where they can be introduced into the engine and burnt during the appropriate stages.

This is managed by means of a solenoid valve which opens and closes the duct to the inlet.

The Engine Management Node implements an adjustment strategy by controlling the value supplied by the Lambda sensor during the canister scavenging stages;

• in the case of excess oxygen in the composition of the exhaust gases (lean mixture), this means that there are no petrol vapours in the canister and therefore the solenoid valve is closed after a short period;
• if there is enrichment of the (rich) mixture, the Engine Management Node keeps the solenoid valve open, allowing the scavenging of the filter and adjusting the injection time. The opening is maintained until there is a variation in the mixture (poor) and then it is closed again. Nominally the filter washing flow rate is limited to percentage points of the air flow rate meter reading so that the adjustment plan is as balanced as possible and the driveability of the vehicle is disturbed as little as possible.

1.2 16v, 1.4 16v

RECOGNITION OF CYLINDER POSITION

The engine timing signal, together with the engine rpm and top dead centre (TDC) signal, allows the control unit to recognize the succession of cylinders to implement phased injection.

This signal is generated by a Hall-effect sensor, positioned on the cylinder head near the phonic wheel on the inlet camshaft.

1.6 16v

Operation during cut-off

The fuel cut-off strategy is implemented when the control unit recognizes the butterfly valve in the idle position and the engine speed is 1350 rpm (variable indicative value).

The control unit only enables the cut-off when the engine temperature exceeds 0° C.

The control unit with engine speed of 1270 rpm (variable indicative value) and butterfly valve in open position, re-enables the fuel supply to the engine.

For very high speeds the cut-off is implemented even when the throttle is not completely closed, but when the pressure in the inlet manifold is particularly low (partial cut-off).

1.8 16v

INJECTION MANAGEMENT

Under these circumstances there is a natural weakening of the mixture because of the reduced evaporation and the strong condensation of the fuel on the inner walls of the inlet manifold.

In addition, the increased viscosity of the lubricant oil causes an increase in the passive resistance of the engine.

Base pulse constant is corrected by a multiplication factor based on temperature and engine speed.

2.4 20v

Control of the maximum rpm

Depending on the rpm reached by the engine, the Engine Management Node:

• over 6800 rpm cuts off the supply to the injectors (it is allowed to reach a maximum of 7000 rpm for a maximum of 3 s).
• below 6600 rpm it restores the operation of the injectors.

1.2 16v, 1.4 16v

FUEL CUT-OFF DURING OVERRUNNING

When the accelerator pedal is released and beyond a preset engine rpm limit, the control unit: * cuts off the supply to the injectors * - reactivates the supply to the injectors at 1300 - 1500 rpm.

As there is no fuel supply, the rpm decreases more or less rapidly depending on the vehicle's driving conditions.

Before idle speed is reached, the trend of the fall in rpm is checked.

If it exceeds a certain value, the fuel supply is partially reactivated so that the engine can 'gently accompany' the drop towards idle speed.

The thresholds for reactivation of the fuel supply and for fuel cut-off vary depending on:

• engine coolant temperature
• vehicle speed
• engine rpm

1.6 16v

Operation during acceleration

During this stage, the control unit increases the quantity of fuel requested by the engine as appropriate (to achieve maximum torque) according to the following signals:

• throttle position;
• rpm and TDC signal

The 'basic' injection time is multiplied by a coefficient which depends on the temperature of the engine coolant, the opening speed of the accelerator butterfly and the increase in pressure in the inlet manifold.

If the sharp variation in the injection time is calculated when the injector is already closed, the control unit reopens the injector (extra pulse) in order to compensate the mixture strength extremely quickly; the subsequent injections are already increased on the basis of the coefficients mentioned previously.

1.8 16v

IGNITION MANAGEMENT

When the engine is running cold, an additional advance correction is carried out: the advance increase over and above the mapped setting is inversely proportional to engine temperature.

a, Crankshaft ponic wheel signals

a, Fixed ignition advance (10° engine)

ON, Coil conduction active

OFF, Coil conduction deactivated

2.4 20v

Check on fuel-electric fuel pump supply

The Engine Management Node supplies the electric pump:

• with ignition in ON position for 5 secs
• ignition in START position and engine speed > 25 rpm

The Engine Management Node cuts off the supply to the electric pump:

• with ignition in OFF position
• with engine speed < 22.8 rpm.

The returnless fuel supply system ensures a constant petrol pressure of 3.5 bar.

1.2 16v, 1.4 16v

FUEL VAPOUR RECOVERY

The (polluting) fuel vapours, collected in an activated-charcoal filter (canister), are sent to the inlet ducts to be burnt.

This takes place via a solenoid controlled by the control unit only when the engine's operating conditions so permit.

The control unit compensates for the additional quantity of fuel by reducing the delivery to the fuel injectors.

1.6 16v

Protection against excess rpm

When the engine rotation speed exceeds 6500 rpm for more than 10 seconds or reaches the 'limit' of 6700 rpm set by the manufacturer for a moment, the engine is operating under 'critcal' conditions.

When the electronic control unit recognizes that the above speed has been exceeded, it prevents the operation of the injectors.

When the rotation speed returns to a non critical value, the operation is resumed.

1.8 16v

OPERATION IN FULL LOAD CONDITIONS

This strategy is enabled when the throttle opening exceeds 70.

Base pulse constant is multiplied by a factor (engine speed operation) equal to 1.1.

2.4 20v

Connection with climate control system

At the power demand, following the switching on of the compressor, the Engine Management Node drives the idle speed actuator to increase the air flow.

The Engine Management Node momentarily interrupts the supply to the compressor:

• during starting
• by switching it off if the engine temperature > 112°C.
• during pick-up with accelerator fully depressed.

1.2 16v, 1.4 16v

CONTROLLING MAXIMUM RPM

Depending on the rpm reached by the engine, the control unit:

• over 7000 rpm cuts off the supply to the fuel injectors
• below 7000 rpm it restores the operation of the injectors.

1.6 16v

Fuel pump control

The electric fuel pump is controlled by the engine control unit by means of a relay.

The pump cuts out:

• if the engine speed goes below about 50 rpm
• after a certain period (about 5 seconds) with the ignition switch in the ON position without the engine being started up (timed go ahead)
• if the inertia switch has operated.

1.8 16v

OPERATION IN ACCELERATION CONDITIONS

During this stage, the control unit increases the quantity of fuel delivered.

Base pulse constant is multiplied by a factor which depends on the temperature of the engine, the opening speed of the accelerator throttle (average value 1.2).

If the sharp variation in the injection time is calculated when the injector is already closed, the control unit reopens the injector (extra pulse) in order to compensate the mixture strength extremely quickly.

The subsequent injections are already increased on the basis of the coefficients mentioned previously.

A, Normal injection time

B, Injector reopening (extra pulse)

C, Injection time including enrichment

OFF, Engine at stationary speed

ON, Engine in transitory condition

2.4 20v

Recognition of cylinder position

During each revolution of the engine, the Engine Management Node recognizes which cylinder is in the combustion stroke and controls the injection sequence at the appropriate cylinder.

In the absence of the timing sensor signal, the Engine Management Node:

• deactivates the detonation sensors
• with the car moving, maintains phased injection
• car does not start with timing sensor faulty

1.2 16v, 1.4 16v

ADJUSTING INJECTION TIMES

The control unit calculates the injector opening times and controls them extremely quickly and precisely on the basis of:

• engine load (rpm and air flow)
• battery voltage
• engine coolant temperature;

Fuel injection is sequential and phased for each cylinder, and takes place at the optimum 'start-of-injection' point, while the 'end-of-injection' point remains fixed.

1.6 16v

Injector control

The operation of the injectors is the sequential, phased type. However, during starting the injectors are operated once in parallel (full-group).

The timing of the injector operation varies according to the engine speed and pressure of the inlet air in order to improve the filling of the cylinders with advantages in terms of consumption, driveability and pollution.

1.8 16v

OPERATION IN DECELERATION CONDITIONS

During this stage a negative transitory strategy is implemented to decrease the quantity of fuel supplied.

The 'basic' injection time is multiplied by a coefficient which depends on the temperature of the engine and the engine speed and load conditions immediately prior to the start of deceleration.

2.4 20v

Regulation of fuel injection times

The Engine Management Node calculates the injector opening times and controls them extremely quickly and precisely on the basis of:

• engine load (rpm and air flow)
• battery voltage
• engine coolant temperature;

Fuel injection is sequential and phased for each cylinder, and takes place at the optimum 'start-of-injection' point, while the 'end-of-injection' point remains fixed.

1.2 16v, 1.4 16v

ADJUSTING IGNITION ADVANCES

Thanks to the mapping stored in its memory, the control unit can calculate the ignition advance in accordance with:

• engine load (idling, choke, full load depending on the rpm and air flow)
• intake air temperature
• engine coolant temperature.

The ignition can be selectively delayed at the required cylinder, which is recognized by means of the combination of the values recorded by the knock and cam angle sensors.

1.6 16v

Check on knocking

The control unit detects the presence of knocking by processing the signal coming from the relevant sensor.

The strategy continuously compares the signal coming from the sensor with a threshold value, which, in turn, is continuously updated to take account of background noise and ageing of the engine.

If the system recognizes the presence of detonation, the strategy reduces the ignition advance until the detonation disappears; the advance ia then gradually reset to the basic value, or until detonation arises again. In particular, advance increases are implemented gradually, whilst reductions are implemented immediately.

Under acceleration conditions, a higher threshold is used to take account of the increased engine noise under such conditions.

The strategy also features a self-adaptation function which temporarily memorizes the reductions in the advance that may be continuously repeated, in order to adjust the advance to the different engine operating conditions (for example, the use of a low octane rating fuel). The strategy is capable of restoring the advance to the threshold value memorized when the conditions which have caused the reduction no longer exist.

1.8 16v

CONTROL OF THE INJECTION

The cut-off strategy is implemented when the control unit identifies throttle idle position (throttle potentiometer signal) and the engine speed exceeds 1600 rpm (with engine warm).

Engine fuel suppy is re-enabled when the ECU identifies the throttle not closed position or when speed drops below 1200 rpm (with engine warm).

2.4 20v

Adjustment of ignition advance values

Thanks to the mapping stored in its memory, the Engine Management Node can calculate the ignition advance in accordance with:

• engine load (idling, choke, full load depending on the rpm and air flow)
• intake air temperature
• engine coolant temperature.

The ignition can be selectively delayed at whichever cylinder requires it, by combining the values recorded by the rpm and timing sensors.

1.2 16v, 1.4 16v

CONTROL OF THE IDLE SPEED

The control unit recognizes the idle condition from the accelerator pedal being in the 'released' position.

According to the consumers switched on and the brake/clutch pedal signals, the control unit controls the position of the motorized butterfly.

The idle speed when warm is 700 ± 50 rpm.

1.6 16v

Management of radiator fan

The control unit directly controls the operation of the radiator fan according to the temperature of the engine coolant and the engagement of the climate control system.

The fan is switched on when the temperature exceeds 97°C (1st speed) and 101°C (2nd speed). The switching off takes place with a hysteresis of 3°C below the engagement threshold.

1.8 16v

CONTROL OF THE IGNITION

Ignition advance is increased when cut-off is imposed. When fuel supply is re-enabled, the advance is gradually restored to base values.

2.4 20v

Control of the idle speed

The Engine Management Node recognizes the idle condition from the accelerator pedal being in the 'released' position.

- According to the consumers switched on and the brake/clutch pedal signals, the Engine Management Node controls the position of the motorized butterfly.

The idle speed when warm is 700 ± 50 rpm. with air conditioner off; with air conditioner on, the idle speed is 770 ± 50 rpm.

1.2 16v, 1.4 16v

CONTROLLING RADIATOR COOLING FAN

The control unit controls the switching on of the electric fan in accordance with the coolant temperature:

• temperature for switching on 1st speed 97°C
• temperature for switching on 2nd speed 101°C

There is a further check (4 stage pressure switch signal) which engages the 1st or 2nd fan speed, according to the pressure of the refrigerant gas, with the air conditioning system switched on.

In the absence of the coolant temperature signal, the control unit activates the recovery function and switches on the fan 2nd speed until the error disappears.

1.6 16v

Engine idle management

The control unit recognizes the idle condition from the accelerator pedal being in the 'released' position. - According to the consumers switched on and the brake/clutch pedal signals, the control unit controls the position of the motorized butterfly.

The idle speed when warm is 700 ± 50 rpm.

1.8 16v

RPM LIMITATION

This strategy limits maximum speed achievable by the engine by enabling cut-off gradually as described below:

• fuel cut off to one cylinder, cylinder 1
• fuel cut off to two cylinders, cylinders 1 and 4
• fuel cut off to three cylinders, cylinders 1, 3 and 4
• fuel cut off to four cylinders, cylinders 1, 2, 3 and 4

The maximum rpm is 7000 rpm.

2.4 20v

Electric engine cooling fan check

Depending on the temperature of the coolant, the Engine Management Node communicates with the fan activation control interface.

The signal consists of a duty cycle that varies continuously on the basis of vehicle speed, coolant temperature and fluid pressure in the air conditioner. Fan speed changes continuously with changes in the duty cycle calculated by the engine management unit.

In the absence of PWM signals, the engine control unit implements a recovery strategy that turns the fan at maximum speed.

1.2 16v, 1.4 16v

VIEW OF ASSEMBLY

The diagram below shows the main components of the system.

1, Speedometer (via CAN network)

2, System failure bulb (via CAN network)

3, CITY button (via CAN network)

4, Engine management control unit

5, Throttle control actuator and throttle position sensor

6, Ignition coils

7, Coolant temperature sensor

8, Radiator fan

9, Lambda sensor (upstream)

10, Lambda sensor (downstream)

11, Injection timing sensor

12, Spark plugs

13, Engine rpm and TDC sensor

14, Knock sensors

15, Injectors

16, Air temperature and absolute pressure sensor

17, Charcoal filter solenoid valve

18, Active charcoal filter

19, Holder (including pump, pressure regulator, filter, level sensor)

20, Inertia switch

21, Battery

22, Ignition switch

23, Engine management system relay

24, Fuel pump relay

25, Radiator fan relay(s)

26, Climate control system connection

27, CODE connection (via CAN)

28, Diagnostic equipment connection (via CAN)

29, Rev counter (via CAN)

1.6 16v

- Warming up stage

The engine speed is corrected, particularly on the basis of the engine coolant temperature.

When the optimum temperature is reached, the idle management depends only on the signal coming from the rpm sensor; when external loads are switched on, the control unit controls the actuator to adjust the rpm to the new conditions and to manage the engine load while maintaining the idle speed.

1.8 16v

OPERATION WITH ENGINE IDLING

When the engine is idling, advance management is implemented independently of the base advance.

The idle advance value, which varies according to the temperature of the coolant (10 with the engine warm) is corrected on the basis of the variation of the speed in relation to the pre-set speed, which also depends on the temperature.

More specifically, the advance is increased if speed falls and reduced if speed increases in order to ensure the speed remains stable.

a, Correction of ignition advance during idling

+ RPM, Idling speed is higher than nominal speed

- RPM, Idling speed is lower than nominal speed

2.4 20v

ACCELEROMETER SENSOR

The accelerometric sensor measures an acceleration value by means of an internal piezoelectric element and generates an output voltage proportional to the intensity of the parameter.

It is used to measure ground roughness and must therefore be fitted very rigidly to the vehicle body in a very specific area: the suspension dome.

We need to measure roughness because we need to discriminate, for the purposes of engine control, between drive torque changes due to road surface roughness and changes due to combustion chamber misfiring.

The accelerometric sensor is essential for Bosch engine testing where the car is not fitted as standard with an ABS, which communicates actively with the Bosch Engine Management Node via a high speed CAN line. In this case, ground unevenness is detected via the speed sensors fitted to individual wheels.

1.2 16v, 1.4 16v

Specifications

The control unit is mounted in the engine bay over the throttle body and withstands high temperatures.

The control unit memory is the 'flash EPROM type, i.e. reprogrammable from the outside without intervening on the hardware.

The replacement of the injection control unit or the throttle body means that the self-learning procedure has to be carried out.

1.6 16v

Management of fuel vapour recirculation

This strategy controls the position of the vapour cut out solenoid valve in the following way:

• during starting the solenoid remains closed, preventing the fuel vapours from enriching the mixture too much; this condition persists until the temperature of the coolant reaches 65° C;
• with the engine up to to temperature, the electronic control unit sends the solenoid a square-wave signal (duty cycle) which modules its opening.

In this way the control unit controls the quantity of fuel vapours sent to the inlet, preventing considerable variations in the mixture strength.

In the condition listed below, the operation of the solenoid valve is inhibitied, maintaining the same in the closed position; this improves engine operation:

• throttle valve in closed position
• engine speed below 1500 rpm
• inlet manifold pressure below the limit calculated by the control unit depending on the number of revs,

1.8 16v

CONTROL OF DETONATION

This strategy has the task of detecting the presence of detonation (engine knock) by processing the signal coming from the relevant sensor.

The strategy continuously compares the signal coming from the sensor with a threshold value, which, in turn, is continuously updated to take account of background noise and ageing of the engine.

If the system recognizes the presence of detonation, the strategy reduces the ignition advance, proceeding in steps of 2 up to a maximum of 7, until the phenomenon disappears.

Later, the advance is gradually restored to the basic value or until the phenomenon occurs again.

In particular, advance increases are implemented gradually, whilst reductions are implemented immediately.

2.4 20v

SPECIFICATIONS

The Engine Management Node, constructed from microhybrid echnology, is fitted on the butterfly casing and is resistant to high temperatures.

The Engine Management Node memory is the 'flash EPROM type, i.e. reprogrammable from the outside without intervening on the hardware.

The adoption of the encrypted code does not allow control units to be exchanged between cars.

1.2 16v, 1.4 16v

CONTROL UNIT PIN-OUT

The diagram below shows

ENGINE SIDE connector (1)

1, Not connected

2, Cylinder 3 injector control

3, Not connected

4, Not connected

5, Not connected

6, Pressure sensor

7, + 5 V sensors

28, Pre-catalyzer Lambda sensor signal (+)

9, Engine timing sensor earth

10, Engine rpm sensor

11, Throttle valve actuator earth

12, Not connected

13, Not connected

14, Not connected

15, Cylinder 4 coil operation

16, Cylinder 2 coil operation

17, Post-catalyzer Lambda sensor signal (+)

18, Cylinder 2 injector control

19, Not connected

20, Not connected

21, Knock sensor signal

22, Not connected

23, Throttle 1 potentiometer signal input

24, Not connected

25, Pre-catalyzer Lambda sensor earth

26, Air temperature and pressure sensor earth

27, Not connected

28, Throttle valve actuator (positive)

29, Not connected

30, Not connected

31, Cylinder 3 coil operation

32, Cylinder 1 coil operation

33, Canister scavenging solenoid valve operation

34, Cylinder 4 injector control

35, Not connected

36, Engine timing sensor signal

37, Knock sensor earth

38, Engine temperature sensor signal

39, Throttle 2 potentiometer signal input

40, Not connected

41, Post-catalyzer Lambda sensor earth

42, Engine rpm sensor

43, Throttle valve actuator earth

44, Not connected

45, Not connected

46, Not connected

47, Not connected

48, Not connected

49, Pre-catalyzer Lambda sensor heater

50, Not connected

51, Cylinder 1 injector control

52, Not connected

53, Not connected

54, Not connected

55, Air temperature sensor

56, Throttle potentiometers 1 and 2 supply (+5V)

57, Post-catalyzer Lambda sensor signal

58, Throttle 1 and 2 potentiometers earth

59, Not connected

60, Throttle valve actuator positive

61, Not connected

62, Not connected

63, Not connected

64, Not connected

VEHICLE SIDE connector (2)

1, Not connected

2, Line k

3, Not connected

4, Accelerator pedal 2 potentiometer supply (+5V)

5, Accelerator pedal 2 potentiometer earth

6, Not connected

7, Clutch switch signal

8, Not connected

9, Not connected

10, Not connected

11, CAN network (HIGH)

12, Not connected

13, Not connected

14, 1st fan speed relay feed

15, Not connected

16, Not connected

17, Power supply from main relay

18, Direct supply (+30)

19, Main relay feed

20, Rev counter signal

21, Accelerator pedal 1 potentiometer supply (+5V)

22, Accelerator pedal 1 potentiometer earth

23, Not connected

24, 2nd fan speed switch engagement (quadrinary)

25, Brake pedal switch signal

26, Not connected

27, Not connected

28, Not connected

29, Not connected

30, 2nd fan speed relay feed

31, Failure warning light on signal

32, Not connected

33, Main relay power supply

34, Not connected

35, Not connected

36, Not connected

37, Accelerator 2 potentiometer signal inpu

38, Failure warning light on request

39, Not connected

40, Air conditioning engagement request

41, Not connected

42, Oil pressure signal

43, CAN network (LOW)

44, Not connected

45, Not connected

46, Air conditioning cmopressor engagement relay control

47, Not connected

48, Not connected

49, Direct supply from main relay

50, Not connected

51, Signal from ignition switch (15/54)

52, Not connected

53, Not connected

54, Accelerator 1 potentiometer signal input

55, Fuel tank level sensor signal

56, 1st fan speed switch operation (quadrinary)

57, Not connected

58, Not connected

59, Not connected

60, Not connected

61, Not connected

62, Petrol pump relay feed

63, Not connected

64, Not connected

1.6 16v

Climate control system management

The injection/ignition control unit is connected to the climate control system in that:

• it receives the request to switch on the compressor and make the related interventions (additional air);
• it gives the go ahead to switch on the compressor, when the conditions covered by the strategies have arisen;
• it receives information relating to the climate control system pressure from the linear sensor and implements the appropriate interventions (radiator fan operation).

If the engine is idling, when the compressor turns on and power is required, the control unit drives the motorized throttle to increase the air flow.

The control unit disengages the compressor:

• if the coolant temperature exceeds a certain threshold
• if the engine rpm is below 700 rpm.

The control unit temporarily controls the disengagement of the compressor (for a few seconds):

• during high power requests from the engine (strong acceleration)
• during engine pickup:

1.8 16v

OPERATION WITH PHASE TRANSFORMER ACTIVATED

When variable valve timing is activated/deactivated, the base advance is adjusted on the basis of speed and engine load.

The control unit controls the variable valve timing hydraulic actuator (fitted on the intake side of the camshaft) via a control relay.

The VVT has two operating conditions:

• OFF position (power, reduced engine idle loads), corresponding to the normal camshaft fitting value.
• ON position (torque) corresponds to a camshaft advance of 25° over the crankshaft.

The VVT, normally off, is set to ON according to engine load and rpm as shown in the figure.

In any case, the ON position is enabled only for coolant temperatures in excess of 40°C.

1, VVT ON

2, Power TP curve (engine load)

3, Maximum speed limitation

2.4 20v

Pin-out

The pin out for connector F of the Engine Management Node is as follows:

F1 - Not connected

F2 - Not connected

F3 - Fiat CODE control unit connection

F4 - Not connected

F5 - Not connected

F6 - Air conditioner control from dashboard

F7 - Accelerator pedal potentiometer power supply

F8 - Signal for potentiometer - 1 accelerator pedal

F9 - Not connected

F10 - Cruise control ON/OFF

F11 - Not connected

F12 - Low CAN line

F13 - Compressor relay control

F14 - Not connected

F15 - +30 power supply

F16 - Main relay power supply

F17 - Not connected

F18 - Not connected

F19 - Not connected

F20 - Not connected

F21 - Not connected

F22 - Not connected

F23 - Not connected

F24 - Potentiometer earth - 1 accelerator pedal

F25 - Earth on accelerator pedal 2 potentiometer/Earth on air conditioner pressure sensor earth/air flow meter earth

F26 - Brake pedal release signal

F27 - Brake pedal pressed signal

F28 - Not connected

F29 - High CAN line

F30 - Fuel pump relay control

F31 - Main relay activation

F32 - Main relay power supply

F33 - Not connected

F34 - Not connected

F35 - Not connected

F36 - Not connected

F37 - Not connected

F38 - Not connected

F39 - Not connected

F40 - Potentiometer signal - 2 accelerator pedal

F41 - Not connected

F42 - Cruise control RCL

F43 - Cruise control SET +

F44 - Not connected

F45 - CAN line 2 'high'

F46 - Injection warning light (EOBD)

F47 - +15 power supply controlled by ignition

F48 - Main relay power supply

F49 - Not connected

F50 - Not connected

F51 - Not connected

F52 - Not connected

F53 - Diagnostic connection (K line)

F54 - Air temperature sensor signal

F55 - Not connected

F56 - Accelerator pedal 2 potentiometer power supply

F57- Air flow meter signal

F58 - Cruise control SET -

F59 -Clutch switch signal

F60 - Oil pressure switch

F61 - Not connected

F62 - Not connected

F63 - Air flow meter power supply (+5V)/Air conditioner pressrue sensor power supply

F64 - Not connected

The pin out for connector M of the Engine Management Node is as follows:

M1 - Throttle motor power supply

M2 - Post catalyzer Lambda sensor heating

M3 - Cylinder 4 injector operation

M4 - Modular manifold solenoid valve

M5 - Fuel vapour solenoid valve operation

M6 - Detonation sensor 2 reference earth

M7 - Not connected

M8 - Not connected

M9 - Not connected

M10 - Engine RPM sensor

M11 - Not connected

M12 - Not connected

M13 - Not connected

M14 - Cylinder 3 coil operation

M15 - Cylinder 4 coil operation

M16 - Cylinder 1 coil operation

M17 - Throttle motor power supply

M18 - Not connected

M19 - Cylinder 1 injector operation

M20 - Cylinder 3 injector operation

M21 - Not connected

M22 - Knock sensor 1

M23 - Pre-catalyzer Lambda sensor signal

M24 - Throttle casing potentiometer 1

M25 - Engine coolant temperature

M26 - Timing sensor earth/Engine temperature sensor earth/Throttle body potentiometer earth

M27 - Not connected

M28 - Post catalyzer Lambda sensor signal

M29 - Not connected

M30 - Not connected

M31 - Cylinder 5 coil

M32 - Cylinder 2 coil

M33 - Throttle valve motor power supply

M34 - Pre-catalyzer Lambda sensor heating

M35 - Cylinder 2 injector operation

M36 - Phase tranformer on/off

M37 - Not connected

M38 - Knock sensor 2

M39 - Not connected

M40 - Throttle body potentiometer 2

M41 - Not connected

M42 - Timing sensor signal

M43 - Not connected

M44 - Not connected

M45 - Not connected

M46 - Not connected

M47 - Not connected

M48 - Not connected

M49 - Throttle valve motor power supply

M50 - Not connected

M51- Timing sensor supply

M52 - Cylinder 5 injector operation

M53 - Not connected

M54 - Knock sensor 1 reference earth

M55 - Pre-catalyzer Lambda sensor earth signal

M56 - Not connected

M57 - Not connected

M58 - Throttle body 2 potentiometer supply

M59 - Engine rpm sensor

M60 - Post catalyzer Lambda sensor earth signal

M61 - Not connected

M62 - Not connected

M63 - Not connected

M64 - Not connected

1.2 16v, 1.4 16v

Specifications

The twin jet injectors (with the spray at an angle in relation to the injector axis) are specifically designed for engines with 4 valves per cylinder, making it possible to direct the jets towards the two inlet valves.

The injector is top-feed, i.e. fuel is fed in from the upper part of the body, which houses the electrical winding connected to the terminals of connector (3).

When the current passes through the winding, the magnetic field which is produced attracts the shutter, opening the injector and the flow of fuel.

Two rings ensure a seal on the fuel manifold side (1) and intake manifold side (2).

Notch (4) determines angular injector position and directs the jets correctlly in relation to the intake valves.

1.6 16v

Air temperature sensor

If the error is present during starting:

• it assumes a value of 50 °C
• self-adjustment of the mixture strength is inhibited.

If the error is present in other conditions:

• the last valid value is memorized and updated according to the engine temperature.

1.8 16v

INTERVENTION STRATEGY

The general aim of this strategy is to keep the engine idling at around the value memorized (engine warm: 850 rpm);

This is achieved by means of the ignition advance and throttle valve that is moved by the control unit to admit more air when rpm drops and less air when rpm rises.

2.4 20v

SPECIFICATIONS

The twin jet fuel injectors are installed on the distribution manifold.

A retainer secures the fuel injectors to the distribution manifold, and two O-rings ensure the seal.

The fuel injectors are responsible for delivering the necessary quantity of fuel to the engine.

They are 'all or nothing' devices, as they can remain in only two stable states, i.e. open or closed. They allow fuel to pass when they are open, while they block delivery when they are closed.

1.2 16v, 1.4 16v

Electrical characteristics

Injector resistance may be measured by disconnecting the connector and connecting an ohmmeter as shown in the figure.

Resistance value: 14.5 ± 5% ohm.

1.6 16v

Knock sensor

If the sensor is faulty, the engine control unit implements more conservative ignition advance 'maps' to safeguard the engine.

1.8 16v

START-UP STAGE

When the key is inserted, the position of the actuator depends on the temperature of the engine and the voltage of the battery (open-loop position).

2.4 20v

SPECIFICATIONS

It is fitted on the thermostatic cup and measures the temperature of the coolant by means of an NTC thermistor which has a negative resistance coefficient.

an NTC thermistor sends the signal to the Engine Management Node which sends the signal for the indicator and the warning light in the instrument panel.

1.2 16v, 1.4 16v

OPERATING

The jets of fuel, at a differential pressure of 4 bar, come out of the injector and are instantly atomized forming two cones.

The control logic for the injectors is the sequential, phased type, in other words the four injectors are operated according to the engine cylinder inlet sequence, whilst the supply for each cylinder can already start during the expansion stroke and continue until the inlet stroke has already started.

1.6 16v

Pressure sensor

If the failure is present during starting, it uses a value of 1024 mbar.

During operation the value used is calculated on the basis of parameters supplied by the throttle valve position sensor and the rpm sensor.

Self-adjustment of the mixture strength is inhibited.

1.8 16v

ENGINE STARTED WITH ACCELERATOR PEDAL RELEASED

The engine speed varies according to the temperature of the engine and is constantly kept close to this value by altering the position of the shutter to compensate for any fluctuations in the speed.

This especially takes place when external loads are switched on (power assisted steering, heated rear windscreen, etc.).

2.4 20v

SPECIFICATIONS

The sensor is based on semiconductor technology; so if the sensor temperature increases as the water temperature increases, the resistance decreases.

As the variation in resistance is not linear, for the same temperature increment, it is higher for low temperatures than for high temperatures.

1.2 16v, 1.4 16v

FUEL MANIFOLD

The function of the fuel manifold is to distribute fuel to the injectors. It incorporates seats for the injectors and air bleed valve.

The fuel intake is secured by a quick-release fitting.

No recirculation pipe is present because the system is returnless.

1, Fuel manifold

2, Injector

3, Fuel inlet connection

4, Bleed valve

1.6 16v

Vehicle speed sensor

The last vehicle speed value memorized is assumed.

1.8 16v

NORMAL DRIVING

The various different correlations between accelerator pedal position and throttle openging depend on the gear engaged.

2.4 20v

SPECIFICATIONS

The two piezoresistive type knock sensors are fitted on the rear part of the cylinder block/crankcase (one between the 1st and 2nd cylinders, the other between the 4th and 5th cylinders) and measure the intensity of the vibrations caused by knock in the combustion chambers.

This phenomenon produces a mechanical effect on a piezoelectric crystal which sends a signal to the Engine Management Node.

On the basis of this input signal, the Engine Management Node reduces the ignition advance until the phenomenon disappears. The advance is then gradually restored to the basic value.

The tightening torque for the bolt fixing the detonation sensor is 1.95 - 2.05 daNm.

1.2 16v, 1.4 16v

Specifications

It is fitted on the thermostatic cup and measures the temperature of the coolant by means of an NTC thermistor which has a negative resistance coefficient.

The table shows the variation in the resistance value according to the temperature

1.6 16v

Coolant temperature sensor

In the case of a fault, the control unit inhibits self-adjustment of the mixture strength and idle.

It sets the last temperature value measured; if this does not correspond to the working temperature, the control unit increases it gradually in accordance to the time since the engine was started until the theoretical 80°C is reached.

In addition when the ignition is switched on, the radiator cooling fan is switched on permanently at the second speed.

1.8 16v

CONTROL OF THE FUEL VAPOUR RECOVERY

This strategy controls carbon filter flushing solenoid position as follows:

• during starting the solenoid remains closed, preventing the fuel vapours from enriching the mixture too much; this conditioner persists until the temperature of the coolant temperature reaches 25° C.
• with the engine warmed up, the control unit operates the solenoid valve in duty-cycle to control the quantity of fuel vapours sent to the inlet depending on the engine speed and load.

the operation of the solenoid valve is disabled, maintaining the same closed position, in the following operating conditons:

• throttle in closed position;
• speed below 1250 rpm;
• engine load (TP = 1 ms).

2.4 20v

OPERATION

The molecules of a quartz crystal feature electrical polarization.

In rest conditions (A) the molecules do not have a particular direction.

When the crystal is subjected to pressure or an impact (B); their direction is all the more marked the greater the pressure to which the crystal is subjected. This direction produces a voltage at the ends of the crystal.

A, Rest position

B, Positin under pressure

1.2 16v, 1.4 16v

Operation

The reference voltage for the NTC element for the injection system is 5 Volt; As the input circuit into the control unit is designed as a voltage divider, this voltage is divided between a resistor located in the control unit and the sensor's NTC resistor.

The control unit is thus able to assess the changes in the sensor's resistance via the changes in voltage, and thus obtain the temperature information.

1.6 16v

IAW 5NF injection/ignition control unit

The control unit is fitted in the engine compatment on the inlet manifold air chamber, and can withstand high temperatures.

It is a digital type with a microprocessor, featuring a high calculation capacity, precision, reliability, versatility and low energy consumption and is maintenance-free.

The task of the electronic control unit is to process the signals coming from the various sensors through the application of software algorithms and control the operation of the actuators (in particular the injectors, ignition coils and idle actuator) in order to ensure optimum engine operation.

The adoption of the Fiat CODE does not allow control units to be exchanged between cars.

1.8 16v

CONTROL OF THE MODULAR MANIFOLD

The control unit controls the modular manifold pneumatic actuator (fitted to the intake manifold) via a control solenoid).

The modular manifold has two settings:

Intake from long ducts (from 2000 rpm to 5400 rpm, at medium-high engine loads).

In this position, the solenoid is not activated and the actuator is in rest position. The throttles are therefore closed and the engine takes in air from the long ducts to achieve high torque at medium speeds;

Intake from short ducts (below 2000 rpm and over 5400 rpm, at medium/high loads).

In this position the solenoid is supplied and it places the actuator in communication with the vacuum reservoir, causing the throttles to open, so the engine draws from the short ducts, to obtain the maximum power.

2.4 20v

SPECIFCATIONS

It is fitted on the cylinder block/crankcase and 'faces' the flywheel on the crankshaft.

It is of the inductive type, i.e. it functions by means of the variation in the magnetic field generated by the passage of the teeth of the phonic wheel (60-2 teeth).

The Engine Management Node uses the rpm sensor to determine rpm and to determine crankshaft angular position.

1.2 16v, 1.4 16v

Components

The diagram illustrates the composition of the sensor

1, NTC resistor

2, Sensor body

3, Electrical connector

1.6 16v

Pin-out

The diagram below shows the control unit pins.

(A) CONNECTOR FOR VEHICLE SIDE WIRING

1 Not connected

2 Accelerator pedal sensor supply

3 Accelerator pedal sensor 2 supply/air conditioning pressure switch

4 Not connected

5 Air conditioning pressure switch

6 Not connected

7 Minimum oil pressure signal

8 Not connected

9 Not connected

10 Serial line K

11 Fiat CODE line

12 Key on and supply controlled by ignition (15/54)

13 Not connected

14 Fan 1 engagement request

15 Accelerator pedal 2 sensor/air conditioning pressure switch earth

16 Direct battery +12V

17 Cruise Control management (optional)

18 Not connected

19 Not connected

20 Two-way CAN line (LOW)

21 Not connected

22 Not connected

23 Not connected

24 Not connected

25 Not connected

26 Air conditioning engagement request

27 Not connected

28 Not connected

29 - Key on and supply controlled by ignition (15/54)

30 Not connected

31 Not connected

32 Not connected

33 Cruise Control management (optional)

34 Brake pedal switch

35 Brake pedal switch

36 Two-way CAN line (LOW)

37 Not connected

38 Not connected

39 Not connected

40 Accelerator pedal potentiometer 2 signal

41 Cruise Control management (optional)

42 Accelerator pedal potentiometer 1 signal

43 Not connected

44 Not connected

45 Not connected

46 Accelerator pedal sensor earth 1

47 Not connected

48 Not connected

49 Not connected

50 Clutch pedal switch signal

51 Two-way CAN line (HIGH)

52 Two-way CAN line (HIGH)

53 Not connected

54 Not connected

55 Fan low speed engagement

56 Not connected

57 Not connected

58 System failure signal output

59 Fan high speed engagement

60 Not connected

61 Not connected

62 Injection system relay feed

63 Not connected

64 Air conditioning engagement

(B) CONNECTOR FOR ENGINE SIDE WIRING

1 Coil 4 operation

2 Not connected

3 Coil 3 operation

4 Not connected

5 Engine crankcase earth

6 Engine crankcase earth

7 Absolute pressure and timing sensor earth

8 Not connected

9 Rpm / TDC sensor positive

10 Not connected

11 Not connected

12 Not connected

13 Absolute pressure and timing sensor power supply (+5V)

14 Not connected

15 DBW supply (motorized throttle ( (+5V)

16 Not connected

17 Coil 1 operation

18 Not connected

19 Coil 2 operation

20 Not connected

21 Engine crankcase earth

22 Engine crankcase earth

23 Rpm/TDC sensor negative

24 Timing sensor signal

25 Not connected

26 Not connected

27 Not connected

28 Not connected

29 Not connected

30 Motorized throttle 2 sensor signal

31 Absolute pressure sensor signal

32 Upstream Lambda heater

33 Cylinder 4 injector operation

34 Cylinder 2 injector operation

35 Motorized throttle 1 sensor earth

36 Coolant temperature sensor earth

37 Not connected

38 Not connected

39 Not connected

40 Not connected

41 Detonation sensor positive

42 Downstream Lambda sensor '+' signal

43 Upstream Lambda sensor '+' signal

44 Motorized throttle 1 sensor signal

45 Coolant temperature signal

46 Not connected

47 Not connected

48 Detonation sensor negative

49 Cylinder 3 injector operation

50 Cylinder 1 injector operation

51 Fuel vapour recovery solenoid valve operation

52 DBW motor negative (motorized throttle)

53 Not connected

54 Not connected

55 Not connected

56 Not connected

57 DBW motor positive (motorized throttle)

58 Downstream Lambda sensor '-' signal

59 Not connected

60 Upstream Lambda sensor '-' signal

61 Not connected

62 Not connected

63 Air temperature signal

64 Downstream Lambda heater

1.8 16v

RADIATOR COOLING FAN CONTROL

The control unit directly controls the operation of the radiator fan according to the temperature of the engine coolant and whether or not there is a climate control system.

There is only one fan which comes on when the temperature of the coolant exceeds 95 °C.

The fan goes off with hysteresis of 2°C on the temperature threshold.

2.4 20v

OPERATING

The passage from full to empty, due to the presence or absence of the tooth, causes a variation in the magnetic flow which is sufficient to generate an induced alternating voltage, resulting from the count of teeth located on a ring (or phonic wheel).

The frequency and amplitude of the voltage sent to the Engine Management Node give the latter the measurement of the speed of the engine.

1 - Brass bush

2 - Permanent magnet

3 - Plastic sensor casing

4 - Coil winding

5 - Polar core

6 - Ring gear or flywheel

7 - Coaxial two-wire cable or electrical connection

1.2 16v, 1.4 16v

Specifications

The piezoelectric type detonation sensor is fitted on the cylinder block/crankcase and detects the intensity of the vibrations caused by the detonation in the combustion chambers.

This phenomenon produces a mechanical repercussion on a piezoelectric crystal which sends a signal to the control unit; on the basis of this signal, the control unit reduces the ignition advance until the phenomenon has disappeared. The advance is then gradually restored to the basic value.

Electrical specifications: resistance: 532-588 ohm at 20°C.

1.6 16v

Specifications

The injectors are the (peak) miniature type with a supply of 12 V and an internal resistance of 13.8 - 15.2 ohm at 20°C.

The injectors are fixed by the manifold which presses them into their housings in the inlet manifold ducts, whilst two rubber seals (1) and (2) seal the inlet manifold and the fuel manifold.

The fuel is supplied from above (3) the injector, which contains the winding (4) connected to the terminals (5) of the electrical connector (6).

During removal-refitting, do not exert force on the fuel injector manifold as this could adversely affect its operation.

1.8 16v

MOTORIZED THROTTLE CASING

This has the task of metering the amount of air supplied to the engine (and consequently the power developed) according to the request from the driver via the accelerator.

The air flow meter (AFM) is incorporated in the throttle body and is hot wire type with by-pass flow measurement.

In the upper part there is a duct parallel to the main flow which contains the heated filament inside.

Part of the intake air flow enters the duct. After flowing through the duct, it emerges from the other end and re-enters the main flow.

Measured air mass is therefore proportional to the overall mass flowing through the meter.

To prevent ice formation around the throttle and the hole leading to the oil vapour recirculation valve, the throttle body is heated with a small amount of coolant coming from the engine thermostat made to circulate in a chamber inside the actual casing.

The throttle valve is moved by means of a DC electric motor. It is controlled by the control unit (ECM), which sends a signal to the electric motor after processing signals from the potentiometer (APS) fitted on the accelerator pedal.

2.4 20v

OPERATING

The distance (gap) for obtaining correct signals, between the end of the sensor and the flywheel, should be between 0.8 and 1.5 mm.

This gap is not adjustable, so if a value outside the tolerance range is measured, check the condition of the sensor and the flywheel.

1 - Maximum magnetic flow

2 - Minimum magnetic flow

3 - Induced alternating voltage trend

1.2 16v, 1.4 16v

Operation

The molecules of a quartz crystal feature electrical polarization.

In rest conditions (A) the molecules do not have a particular direction.

When the crystal is subjected to pressure or an impact (B), they are directed - the higher the pressure to which the crystal is subjected, the more marked their direction.

This direction produces a voltage at the ends of the crystal.

A. Rest position

B. Under pressure position

1.6 16v

Operation

The fuel jet at the absolute pressure of 3.5 bar, by means of the returnless system, emerges from the injector and is instantly atomized.

The control logic for the injectors is the sequential, phased type, in other words the four injectors are operated according to the inlet sequences.

1.8 16v

ACCELERATOR PEDAL POTENTIOMETER

The accelerator pedal potentiometer is three-track. The redundant elements are essential to ensure safety.

The control unit is able to recognise an error by monitoring a signal from each track and the correlation between all three signals. It then imposes an emergency strategy.

The throttle position potentiometer (TPS) is two-track. In this case too, the control unit is able to detect errors by monitoring two signals and the correlation between them and then introducing a correction strategy.

At each key on and key off, the control unit initialises the throttle idle position (electrical signal with throtte fully closed).

During this operation, the control unit forces the throttle to the closed position and the sound of the throttle clicking against its seat can be heard.

Idle speed is controlled directly by the control unit, which controls throttle opening (and thus speed) on the basis of the coolant.

1, Engine control circuit

2.4 20v

SPECIFICATIONS

Hall effect; it is mounted on the cylinder head and 'facing' the exhaust camshaft pulley.

1.2 16v, 1.4 16v

Specifications

It is mounted on the engine block and 'faces' the phonic wheel located on the crankshaft.

It is of the inductive type, i.e. it functions by means of the variation in the magnetic field generated by the passage of the teeth of the flywheel (60-2 teeth).

The fuel injection control unit uses the rpm sensor to:

• determine the speed of rotation
• determine the angle of the crankshaft.

Electrical specifications: resistance:1134-1386 ohm at 20°C.

The distance (gap) for obtaining correct signals, between the end of the sensor and the flywheel, should be between 0.5 and 1.5 mm.

1.6 16v

SPECIFCATIONS

The fuel manifold is fixed to the inner part of the inlet manifold and its function is to send the fuel to the injectors.

On the fuel manifold, in addition to the fuel injector seats, there is a rapid attachment for connection with the fuel supply pipe and an attachment for checking the fuel supply pressure.

1, Fuel manifold

2, Injector

3, Attachment for fuel drainage pressure

4, Rapid connector for fuel pipe

1.8 16v

ENGINE RPM SENSOR

It is fitted on the engine block, where it faces the phonic wheel located on the crankshaft.

It is of the inductive type, i.e. it functions by means of the variation in the magnetic field generated by the passage of the flywheel teeth.

The control unit uses the rpm sensor signal for determining the rotation speed and for determning the angular position of the crankshaft.

The engine control unit also uses the rpm signal to detect misfiring or partial firing.

2.4 20v

SPECIFICATIONS

It is fitted on the inlet chamber and regulates the quantity of air drawn in by the engine.

According to the signal coming from the accelerator pedal potentiometer, the Engine Management Node controls the opening of the throttle by means of a direct current motor integrated in the throttle body integrated with D.V.L.

The throttle opening takes place between 0° and 80° therefore including the idle adjustment.

The throttle body integral with D.V.E. is equipped with two potentiometers integrated so that one controls the other and viceversa.

If both the potentiometers fail or there is no supply, depending on the position of the accelerator pedal, the Engine Management Node reduces the drive torque:

• with the pedal fully depressed, it cuts off the supply to one or more pistons, until a maximum speed of 2500 rpm is reached.
• with the pedal in intermediate positions, it cuts off the supply to one or more pistons, until a speed below 1200 rpm is reached.

If the throttle body with D.V.E. incorporated is replaced, then the self-learning procedure has to be carried out.

1.2 16v, 1.4 16v

Components

The sensor consits of a tubular casing (1) which contains a permanent magnet (3) and an electrical winding (2).

1.6 16v

Specifications

This is mounted on the thermostatic cup, and it measures the coolant temperature by means of an NTC thermistor with a negative resistance coefficient.

1.8 16v

SPECIFCATIONS

It is fitted in the engine compartment and is resistant to high temperatures.

It is a digital type with a microprocessor, featuring a high calculation capacity, precision, reliability, versatility and low energy consumption and is maintenance-free.

The task of the electronic control unit is to process the signals coming from the various sensors through the application of software algorhythms and control the operation of the actuators (in particular, the injectors, ignition coils and idle actuator) in order to ensure optimum engine operation.

The adoption of the Fiat CODE does not allow control units to be exchanged between cars.

2.4 20v

SPECIFICATIONS

The flow meter is located on the air inlet duct and is of the 'hot film' type.

1.2 16v, 1.4 16v

Operation

As the flywheel teeth go past, the magnetic flow produced by the magnet (3) undergoes fluctuations due to the change in the gap.

These fluctuations induce an electromotive force in the winding (2), at the ends of which there is a voltage which alternates between positive (tooth opposite sensor) and negative (gap opposite sensor).

1, Sensor

2, Output signal

3, Signal corresponding to the two missing teeth

4, Crankshaft pulley with flywheel

1.6 16v

Electrical characteristics

1.8 16v

Injection/ignition control unit PIN OUT

The diagram below illustrates the control unit pin out.

Connector A

1, Cylinder 1 injector operation

2, Cylinder 2 injector operation

3, Cylinder 3 injector operation

4, Cylinder 4 injector operation

5, Power earth

6, Power earth - 1

7, Cylinder 1 coil control

8, Cylinder 2 coil control

9, Cylinder 3 coil control

10, Cylinder 4 coil control

11, Not connected

12, Not connected

13, Air flow meter earth

14, Air flow meter signal

15, Not connected

16, Not connected

17, Not connected

18, Throttle potentiometer power supply-1

19, Potentiometer - 1 throttle body

20, Throttle potentiometer reference earth - 1

21, Throttle potentiometer power supply -2

22, Potentiometer - 2 throttle body

23, Throttle potentiometer reference earth - 2

24, Not connected

25, Not connected

26, Engine coolant temperature sensor earth

27, Coolant temperature sensor signal

28, Not connected

29, Knock sensor signal

30, Knock sensor earth

31, Not connected

32, Earth

33, Engine timing sensor signal

34, Engine timing sensor negative

35, Not connected

36, Engine rpm sensor positive

37, Engine rpm sensor negative

38, Engine rpm sensor shield

39, Not connected

40, Earth

41, Earth

42, Not connected

43, Charcoal filter solenoid valve control

44, Power earth - 2

45, Modular manifold solenoid valve control

46, Not connected

47, Variable valve timing electromagnet control

48, Not connected

49, Not connected

50, Not connected

51, Not connected

52, Not connected

53, Not connected

54, Not connected

55, Not connected

56, Not connected

57, Not connected

58, Earth

59, Throttle motor power supply

60, Throttle motor earth

Connector B

1, Power supply from main relay

2, Power supply from main relay

3, Power supply from main relay

4, Control unit supply (+30)

5, Not connected

6, Engine started signal from ignition key +50

7, Fuel pump relay operation

8, System failure bulb control

9, Air conditioning compressor on signal

10, Air conditioning compressor relay control

11, Main relay control

12, Not connected

13, Not connected

14, Fan low speed relay operation

15, Fan high speed relay operation

16, Not connected

17, Not connected

18, Not connected

19, Lambda sensor signal (1 - preconverter)

20, Lambda sensor signal (2 - preconverter)

21, Lambda sensor negative

22, Lambda sensor signal (postconverter)

23, Min. oil pressure signal

24, Control unit supply (+15)

25, Not connected

26, Outfit selection (earthed on ly for versions without a/c)

27, Signal to 4 stage pressure switch

28, Signal to 3/4 stage pressure switch

29, Not connected

30, Not connected

31, Not connected

32, Line k

33, Not connected

34, Not connected

35, Not connected

36, Not connected

37, CAN A line

38, CAN B line

39, Not connected

40, Not connected

41, Not connected

42, Not connected

43, Not connected

44, Supply for potentiometer - 1 accelerator pedal

45, Signal for potentiometer - 1 accelerator pedal

46, Earth for potentiometer - 1 accelerator pedal

47, Supply for potentiometer - 2 accelerator pedal

48, Signal for potentiometer - 2 accelerator pedal

49, Earth for potentiometer - 2 accelerator pedal

50, Supply for potentiometer - 2 accelerator pedal

51, Signal for potentiometer - 2 accelerator pedal

52, Earth for potentiometer - 2 accelerator pedal

53, Not connected

54, Not connected

55, Not connected

56, Not connected

57, Not connected

58, Earth for Lambda sensor heater (1 - preconverter)

59, Earth for Lambda sensor heater (2 - preconverter)

60, Earth for Lambda sensor heater (postconverter)

2.4 20v

SPECIFICATIONS

The intake air temperature sensor is built into the flow meter.

The air flow meter cannot be dismantled.

1 - Covers

2 - Electronic card

3 - Sensor

4 - Support plate

5 - Support

6 - O-ring

7 - Temperature sensor

1.2 16v, 1.4 16v

Operation

The peak value of the output voltage from the sensor, provided other factors remain the same, depends on the distance between the sensor and tooth (gap).

The phonic wheel comprises sixty teeth, two of which have been removed to create a reference: the pitch of the wheel thus corresponds to an angle of 6° (360° divided by 60 teeth).

The synchronization point is recognized at the end of the first tooth after the space created by the two missing teeth: when this passes under the sensor, the pair of pistons 1-4 of the engine are at 114 degrees before TDC.

1.6 16v

Operation

The reference voltage for the NTC element for the injection system is 5 Volt; as the input circuit into the control unit is designed as a voltage divider, this voltage is divided between a resistor located in the control unit and the sensor's NTC resistor.

The control unit is thus able to assess the changes in the sensor's resistance via the changes in voltage, and thus obtain the temperature information.

1.8 16v

Type

The injector has the task of supplying the quantity of fuel required for the operation of the engine: the fuel is injected into the inlet manifold, immediately upstream of the inlet valves.

The injector is the top-feed, twin jet type with the fuel supply from the top part of the casing where the electrical winding connected to the connector terminals is housed.

2.4 20v

OPERATION

The operating principle is based on a heated diaphragm located in a measuring duct through which the intake air entering the engine flows.

The hot film diaphragm is kept at a constant temperature (about 120°C above the incoming air temperature) by the heating resistor.

The air mass passing through the measuring duct tends to draw heat from the diaphragm, so to keep the latter at a constant temperature, some current must flow through the resistor.

This current is measured by a suitable Wheatstone bridge.

The current is therefore proportional to the mass of flowing air.

The flow meter directly measures the air mass (not volume), thus eliminating problems of temperature, altitude, pressure, etc.

1.2 16v, 1.4 16v

SPECIFCATIONS

The accelerator pedal has two built-in potentiometers: * - one main on * - one safety one.

The injection control unit implements the following 'recovery' strategies in the following conditions:

• if there is a fault with one of the two potentiometers, a throttle opening of up to 40° is allowed for a long period
• if both of the potentiometers fail completely, the throttle opening is excluded.

1.6 16v

Components

The components which make up the sensor are:

1, N.T.C. resistor

2, Sensor body

3, Electrical connector

1.8 16v

Introduction

When the current passes through the winding, the magnetic field which is produced attracts the shutter, opening the injector and the flow of fuel.

Two seals work on the fuel manifold side (1) and the inlet manifold side (2).

A reference mark (5) determines the angular position of the injector in relation to the inlet manifold to ensure the correct direction of the jets in relation to the inlet valves.

The injector resistance value is 14.5 ± 5% Ohm.

1, Fuel manifold side seal

2, Inlet manifold side seal

3, Electrical winding

4, Electrical connection

5, Position reference

2.4 20v

SPECIFICATIONS

The ignition circuit is the inductive discharge, static advance type where the high tension is supplied by five coils mounted directly on the spark plugs (pencil-coils).

The coil used is closed magnetic circuit type. The windings are located in a plastic container and embedded in epoxy resin. The coil is connected directly to the spark plug via a silicon extension with good dielectric properties.

The coil incorporates the power transistor for interruption of the primary winding.

1.2 16v, 1.4 16v

Operation

The sensor consists of a casing, secured to the accelerator pedal mount, which contains a shaft, in an axial position, connected to the twin track poteniometer.

There is a coil spring on the shaft which guarantees the correct resistance to the pressure whilst a second spring ensures the return on release.

Operating range from 0° to 70°; mechanical stop at 88°.

1.6 16v

Specifications

The piezoelectric type detonation sensor is fitted on the cylinder block/crankcase and detects the intensity of the vibrations caused by the detonation in the combustion chambers.

This phenomenon produces a mechanical repercussion on a piezoelectric crystal which sends a signal to the control unit; on the basis of this signal, the control unit reduces the ignition advance until the phenomenon (detonation) has disappeared.

The advance is then gradually restored to the optimum basic operating value.

1.8 16v

Type

It is made from aluminium die-casting and incorporates the seats for the injectors and the bleed valve.

It is fixed to the inlet manifold and is responsible for distributing the fuel to the injectors.

1, Fuel manifold

2, Injectors

3, Bleed valve

4, Fuel inlet connector

2.4 20v

Operation

The primary winding of each coil is supplied at battery voltage (+30) via the dual relay and earthed via the power transistor. The transistor base is connected to the relevant Engine Management Node pin.

When the transistor base current is cut, the primary winding earth connection is also cut and a high voltage discharge takes place on the secondary winding.

The Engine Management Node computes the optimal ignition advance on the basis of engine speed and load. The advance is implemented as the time between the exhaust stage TDC and the instant at which the power supply is cut off in the coil primary winding.

1.2 16v, 1.4 16v

SPECIFCATIONS

It is fitted on the inlet chamber and regulates the quantity of air drawn in by the engine.

According to the signal coming from the accelerator pedal potentioemter, the injection control unit controls the opening of the throttle by mens of a direct current motor integrated in the throttle casing.

The throttle opening takes place between 0° and 80° therefore including the idle adjustment. The throttle body actuator is equipped with two potentiometers integrated so that one controls the other and viceversa.

If both the potentiometers fail or there is no supply, depending on the position of the accelerator pedal, the control unit reduces the drive torque:

• fully depressed, it cuts off the supply to one or more pistons, until a maximum speed of 2500 rpm is reached
• in intermediate positions, it cuts off the supply to one or more pistons, until a speed below 1200 rpm is reached.

If the throttle body or the injection control unit or the air chamber is replaced then the self-learning procedure must be carried out.

1.6 16v

Operation

The molecules of a quartz crystal feature electrical polarization.

In rest conditions (A) the molecules do not have a particular direction.

When the quartz crystal is subjected to pressure or an impact (B), they are directed - the higher the pressure to which the crystal is subjected, the more marked their direction.

This direction produces a voltage at the ends of the crystal.

A, Rest position

B, Positin under pressure

1.8 16v

Type

It is fitted on the thermostatic cup and measures the temperature of the coolant by means of an NTC thermistor which has a negative resistance coefficient.

One NTC thermistor sends the signal to the injection control unit whilst the other one sends the signal to the temperature gauge and warning light in the instrument panel.

2.4 20v

ACCELERATOR PEDAL POTENTIOMETER

The accelerator pedal potentiometer is three-track. The redundant elements are essential to ensure safety.

The control unit is able to recognise an error by monitoring a signal from each track and the correlation between all three signals. It then imposes an emergency strategy.

The throttle position potentiometer (TPS) is two-track. In this case too, the control unit is able to detect errors by monitoring two signals and the correlation between them and then introducing a correction strategy.

At each key on and key off, the control unit initialises the throttle idle position (electrical signal with throtte fully closed).

During this operation, the control unit forces the throttle to the closed position and the sound of the throttle clicking against its seat can be heard.

Idle speed is controlled directly by the control unit, which controls throttle opening (and thus speed) on the basis of the coolant.

1.2 16v, 1.4 16v

OPERATING

The throttle opening is managed by an electronic motor.

The ME73H4 system operates the motorized throttle according to the accelerator pedal request; a potentiometer is connected to it which sends a voltage signal to the control unit where it is processed and the more or less accentuated opening laws are produced.

In six-speed versions and automatic transmission versions; the system is able to govern throttle movement in accordance with two modes: one more sporty and the other more comfortable.

The driver can modify the response of the engine to the action of the accelerator pedal via a switch in the console near the gear lever.

In particular:

• with the 'CITY function switched on, the response of the throttle movement is smoother.
• with the 'CITY function switched off, the throttle movement response is faster.

Activation mode:

• press the CITY button;
• release the accelerator pedal.

The control unit activates the management.

The graph illustrates the throttle opening law.

1.6 16v

Electrical characteristics

resistance: 532-588 ohm at 20°C.

1.8 16v

Type

The sensor is based on semiconductor technology; so if the sensor temperature increases as the water temperature increases, the resistance decreases.

As the variation in resistance is not linear, for the same temperature increment, it is higher for low temperatures than for high temperatures.

1.2 16v, 1.4 16v

Specifications

The intake air temperature and pressure sensor is a component which is designed to measure the pressure and the temperature of the air inside the inlet manifold.

Both pieces of information are used by the injection control unit to define the quantity of air drawn in by the engine; this information is then used to calculate the injection time and the point of ignition.

The sensor is fitted on the inlet manifold.

1.6 16v

Specifications

It is fitted on the cylinder block/crankcase and 'faces' the phonic wheel on the crankshaft pulley.

It is of the inductive type, i.e. it functions by means of the variation in the magnetic field generated by the passage of the flywheel teeth (60 - 2 teeth).

The fuel injection control unit uses the rpm sensor to:

• determine the crankshaft rotation speed
• determine the angle of the crankshaft.

1.8 16v

Type

It is the piezoelectric type, fitted on the cylinder block/crankcase in a symmetrical position in relation to the pairs of cylinders 1-2 and 3-4 to detect the onset of detonation in the same way in all cylinders.

It measures the intensity of the vibrations caused by detonation in the combustion chamber.

This phenomenon produces a mechanical effect on a piezoelectric crystal which sends a signal to the control unit;

1.2 16v, 1.4 16v

COMPOSITION

The air temperature sensor consists of an NTC thermistor (Negative Temperature Coefficient). The resistance of the sensor decreases as the temperature increases.

The control unit input circuit divides the 5 Volt reference voltage between the sensor resistance and a fixed reference value, obtaining a voltage which is proportional to the resistance and therefore to the temperature.

The sensitive element of the pressure sensor consits of a Wheatstone bridge on a cermamic diaphragm. On one side of the diaphragm is the absolute reference vacuum, whilst on the other side there is the vacuum from the inlet manifold.

The (piezoresistive) signal from the distortion suffered by the diaphragm, before being sent to the engine control unit, is amplified by an electronic circuit in the support which also houses the ceramic diaphragm.

When the engine is off, the diaphragm bends in accordance with the atmospheric pressure; the altitude information is thus obtained.

When the engine is running, the effect of the vacuum produces a mechanical action on the sensor diaphgram, which bends, altering the resistance value.

Since the supply is kept rigorously constant (5V) by the control unit, altering the resistance alters the voltage output value.

1.6 16v

Components

The sensor consits of a tubular casing (1) which contains a permanent magnet (3) and an electrical winding (2).

1.8 16v

Introduction

The molecules of a quartz crystal feature electrical polarization.

In rest conditions (A) the molecules do not have a particular direction.

When the crystal is subjected to pressure or an impact (B); their direction is all the more marked the greater the pressure to which the crystal is subjected. This direction produces a voltage at the ends of the crystal.

A, Rest position

B, Positin under pressure

1.2 16v, 1.4 16v

Electrical characteristics

The diagram below illustrates the electrical specifications of the sensor.

1.6 16v

Operation

As the flywheel teeth go past, the magnetic flow produced by the magnet (3) undergoes fluctuations due to the change in the gap.

These fluctuations induce an electromotive force in the winding (2), at the ends of which there is a voltage which alternates between positive (tooth opposite sensor) and negative (gap opposite sensor).

The peak value of the output voltage from the sensor, provided other factors remain the same, depends on the distance between the sensor and tooth (gap).

The phonic wheel comprises sixty teeth, two of which have been removed to create a reference: the pitch of the wheel thus corresponds to an angle of 6° (360° divided by 60 teeth).

The synchronization point is recognized at the end of the first tooth after the space created by the two missing teeth: when this passes under the sensor, the pair of pistons 1-4 of the engine are at 114 degrees before TDC.

1, Sensor

2, Output signal

3, Signal corresponding to the two missing teeth

4, Crankshaft pulley with flywheel

1.8 16v

Type

The engine timing signal, together with the engine rpm signal, allow the control unit to recognize the succession of cylinders to implement the phased injection.

This signal is produced by a HALL effect sensor, fitted by the exhaust camshaft drive pulley.

The angular position of the sensor cannot be adjusted in any way.

1.2 16v, 1.4 16v

COMPOSITION

The coils are connected directly to the spark plugs and are the closed magnetic circuit type with a core made from silicon steel with a thin gap containing both windings.

The windings are covered by a pressed plastic container and are insulated through immersion in an epoxy resin and quartz compound which gives them exceptional dielectric, mechanical and thermal properties enabling them to withstand high temperatures. The proximity of the primary winding to the magnetic core reduces the magnetic flow losses optimizing the coupling with the secondary winding.

1.6 16v

Electrical characteristics

resistance: 1134-1386 ohm at 20°C.

The distance (gap) for obtaining correct signals, between the end of the sensor and the flywheel, should be between 0.5 and 1.5 mm.

1.8 16v

Introduction

A semiconducting layer, through which current passes, immersed in a perpendicular magnetic field (force lines perpendicular to the current direction), generates at its ends a difference in potential known as Hall voltage.

If the intensity of the current remains constant, the voltage generated only depends on the intensity of the magnetic field. The intensity of the field therefore simply has to vary periodically to produce a modulated electrical signal.

In practice, to achieve this change, a metal ring (fixed to the inner part of the timing pulley) with a series of openings is passed through the sensor: as it moves, when the ring covers the sensor it blocks the magnetic field and the signal remains low, whilst corresponding to the openings, the field is enclosed and the signal becomes high.

The alternating of the signals therefore depends on the succession of the openings.

1, Deflector

2, Magnetic material

3, Gap

1.2 16v, 1.4 16v

Electrical characteristics

Primary circuit resistance: 0.52-0.62 ohm at 23°C

Secondary circuit resistance: 0.52-0.62 ohm at 23°C

1.6 16v

SPECIFICATIONS _ - The accelerator pedal has two built-in potentiometers: * - one main on * - one safety one.

The injection control unit implements the following 'recovery' strategies in the following conditions:

• if there is a fault with one of the two potentiometers, a throttle opening of up to 40° is allowed for a long period
• if both of the potentiometers fail completely, the throttle opening is excluded.

1.8 16v

Type

The ignition circuit is the inductive discharge, static type where the high tension is supplied by four coils mounted directly on the spark plugs (pencil-coils).

The coil used is closed magnetic circuit type. The windings are located in a plastic container and embedded in epoxy resin. The coil is connected directly to the spark plug via a silicon extension with good dielectric properties.

The coil incorporates the power transistor for interruption of the primary winding.

1.2 16v, 1.4 16v

SPECIFCATIONS

This sensor is located at the differential output, by the left driveshaft joint and transmits the vehicle speed to the body computer, which forwards it to the control unit: the signal is also used for the operation of the speedometer.

The Hall effect sensor transmits 16 impulses/rev; according to the frequency of the impulses it is possible to ascertain the speed of the vehicle.

on versions with ABS, the vehicle speed signal is generated by the ABS control unit.

1.6 16v

Operation

The sensor consists of a casing, secured to the accelerator pedal mount, which contains a shaft, in an axial position, connected to the twin track poteniometer.

There is a coil spring on the shaft which guarantees the correct resistance to the pressure whilst a second spring ensures the return on release.

Operating range from 0° to 70°; mechanical stop at 88°.

1.8 16v

Introduction

The primary winding of each coil is supplied at battery voltage (+30) via the dual relay and earthed via the power transistor. The transistor base is connected to the relevant control unit pin.

When the transistor base current is cut, the primary winding earth connection is also cut and a high voltage discharge takes place on the secondary winding.

The optimum ignition advance is calculated by the control unit according to the engine speed and load and is implemented in the form of the time between the TDC during the explosion stroke and the moment the supply for the coil primary winding circuit is interrupted.

1, Cylinder 1 coil

2, Cylinder 2 coil

3, Cylinder 3 coil

4, Cylinder 4 coil

5, Interface connector

6, Engine earth

1.6 16v

SPECIFCATIONS

It is fitted on the inlet chamber and regulates the quantity of air drawn in by the engine.

According to the signal coming from the accelerator pedal potentioemter, the injection control unit controls the opening of the throttle by mens of a direct current motor integrated in the throttle casing.

The throttle opening takes place between 0° and 82° therefore including the idle adjustment. The throttle body actuator is equipped with two potentiometers integrated so that one controls the other and viceversa.

If both the potentiometers fail or there is no supply, depending on the position of the accelerator pedal, the control unit implements a recovery strategy with the resulting inferior operation noticeable to the driver and the EOBD diagnosis is disabled.

If the throttle body integrated with D.V.E. or the injection control unit or the air chamber is replaced then the self-learning procedure must be carried out.

OPERQATION _ -The throttle opening is managed by an electronic motor.

The Marelli 5NF system operates the motorized throttle according to the accelerator pedal request; a potentiometer is connected to it which sends a voltage signal to the control unit where it is processed and the more or less accentuated opening laws are produced.

The position of the throttle is controlled by the control unit by means of a potentiometer built into the throttle casing.

Specifications

The intake air temperature and pressure sensor is a component which is designed to measure the pressure and the temperature of the air inside the inlet manifold. Both pieces of information are used by the injection control unit to define the quantity of air drawn in by the engine; this information is then used to calculate the injection time and the point of ignition. The sensor is fitted on the inlet manifold.

Specifications

The air temperature sensor consists of an NTC thermistor (Negative Temperature Coefficient). - The resistance of the sensor decreases as the temperature increases. The control unit input circuit divides the 5 Volt reference voltage between the sensor resistance and a fixed reference value, obtaining a voltage which is proportional to the resistance and therefore to the temperature.

The sensitive element of the pressure sensor consits of a Wheatstone bridge on a cermamic diaphragm.

On one side of the diaphgram is the absolute reference vacuum, whilst the vacuum from the inlet manifold acts on the other side. The (piezoresistive) signal from the distortion suffered by the diaphragm, before being sent to the engine control unit, is amplified by an electronic circuit in the support which also houses the ceramic diaphragm. When the engine is off, the diaphragm bends in accordance with the atmospheric pressure; the altitude information is thus obtained.

When the engine is running, the effect of the intake pressure produces a mechanical action on the sensor diaphgram, which bends, altering the resistance value. Since the supply is kept rigorously constant (5V) by the control unit, altering the resistance alters the voltage output value.

Electrical characteristics

The diagram below shows the electrical characteristics of the pressure and intake air temperature sensor.

COMPOSITION

The coils are connected directly to the spark plugs and are the closed magnetic circuit type with a core made from silicon steel with a thin gap containing both windings.

The windings are covered by a pressed plastic container and are insulated through immersion in an epoxy resin and quartz compound which gives them exceptional dielectric, mechanical and thermal properties enabling them to withstand high temperatures. The proximity of the primary winding to the magnetic core reduces the magnetic flow losses optimizing the coupling with the secondary winding.

Electrical characteristics

Primary circuit resistance: 0.52-0.62 ohm at 23°C

Secondary circuit resistance: 0.52-0.62 ohm at 23°C

SPECIFCATIONS

The sensor is located at the differential output, near the left drive shaft joint, and transmits the vehicle speed signal to the body computer; the body computer then makes this signal available on the CAN network.

The control unit obtains the vehicle speed information: the signal is also used for the operation of the speedometer.

The Hall effect sensor transmits 16 impulses/rev; according to the frequency of the impulses it is possible to ascertain the speed of the vehicle.

on versions with ABS, the vehicle speed signal is generated by the ABS control unit, and it transmits the information to the body computer which makes it available to the fuel injection control unit via the CAN network.

SPECIFCATIONS

This system uses a sequential phased injection system, i.e. the fuel injection takes place in sequence for each cylinder at the intake stage.

To do this, in addition to the rpm and TDC signal, the electronic unit also uses another signal to determine the injection point. The signal sent to the control unit is produced by a Hall-effect sensor (2) mounted level with the inlet side camshaft drive pulley.

1, Fixing bolts

2, Hall-effect sensor

3, Inlet side camshaft pulley

Principle of operation

A semiconducting layer, through which current passes, immersed in a perpendicular magnetic field (force lines perpendicular to the current direction), generates at its ends a difference in potential known as Hall voltage.

If the intensity of the current remains constant, the voltage generated only depends on the intensity of the magnetic field; the intensity of the field simply has to vary periodically to produce a modulated electrical signal, whose frequency is proportional to the speed with which it changes magnetic field.

To obtain this change, a metal ring (the inside of the pulley) with a series of openings passes through the sensor. As it moves, the metal part of the ring covers the sensor, blocking the magnetic field, resulting in a low output signal; viceversa, level with the gap and so when the magnetic field is present, the sensor generate a high signal.

The alternating of the signals therefore depends on the succession of the openings.

1, Supply (+)

2, Signal output

3, Earth (-)

5, Deflector

6, Magnetic material

7, Gap