Ford Workshop Service and Repair Manuals

Principles of Operation

European On-Board Diagnostics

European On-Board Diagnostics (EOBD) is a diagnostic system integrated into the powertrain control module (PCM). This system continuously monitors vehicle emission components. The system includes a malfunction indicator lamp (MIL) which indicates when there is a concern that can affect emissions or the system malfunctions. Data stored within the module DTC memory can be accessed using a generic scan tool or WDS.

EOBD is mandated within European Union regulations from the year 2003 for passenger vehicles with diesel engines.

EOBD Functions:

• Establishes when and how emissions control faults must be indicated.
• Actuates emission control malfunction indicator lamp (MIL) and fault memory.
• Indicates operating conditions in which the concern occurred (freeze frame data).
• Standardized output of operating data such as engine speed, engine coolant temperature etc.
• Standardized names/abbreviations for components and systems.
• Standardized DTCs for all manufacturers.
• Standardized communication with the diagnostic equipment.
• Standardized 16-pin data link connector (DLC) in area of the instrument panel.
• Concern display must be possible using a generic scan tool.

EOBD consists of the following elements:

Drive Cycle

A drive cycle commences when the engine is started (cold or warm) and ends when the engine is switched off.

Trip

A trip begins when the engine is started and is complete when all the EOBD monitors have completed a self-test. This may take place over a number of drive cycles. On diesel variants, the information gathered from one drive cycle is not carried over to a subsequent cycle or cycles.

When a concern has been rectified, particularly after electronic engine control components have been changed, the DTC memory, which is part of the keep alive memory (KAM) must be cleared of all trouble codes. When the DTC memory has been cleared, the code P1000 (known as the readiness code) is set in the PCM memory, which indicates that since the KAM has been cleared, not all of the monitoring systems have completed their tests. P1000 can only be cleared by carrying out a trip, which includes driving the vehicle under variable conditions of speed, load and time so that all of the monitors are completed. As P1000 will not illuminate the MIL it is not necessary to carry out the trip before returning the vehicle to the customer.

Warm-up Cycle

The warm-up cycle is an operation that consists of key on, engine start and a coolant temperature increase of 22°C, exceeding 71°C on completion.

Freeze Frame Data

When a concern is detected, the following data is stored depending on application including:

• Diagnostic trouble code.
• Vehicle speed.
• Engine coolant temperature.
• Engine speed.
• Engine load.
• Mixture formation trim value (trim value for engine wear).
• Distance covered since the concern was first registered.

Monitors

The purpose of the monitors is to continuously check the operation of the emission related sensors and actuators. It then establishes if they are operating within specified tolerances. All monitors carry out their functions in such a way as to be unnoticeable by the driver of the vehicle. All of the monitors operate under normal driving conditions: There are no monitors which intervene and cause special operating modes to enable the monitors to work. Some diesel monitors are non-continuous. This means that in a drive cycle, monitoring is done as and when suitable driving conditions exist and potential faults are accumulated and compared with acceptance criteria. Examples of this type are the turbocharger boost pressure and Exhaust gas recirculation (EGR) monitors on vehicles with common rail fuel injection.

Comprehensive Component Monitor (CCM)

When the CCM detects a component operating out of tolerance, it sets a Diagnostic Trouble Code (DTC), which is stored in the KAM. If the same concern is confirmed during the next trip the MIL will be switched on. The CCM monitors many components, sub-systems and signals. The following is a list of those that can effect emissions depending on application:

• Crankshaft Position (CKP) signal
• Camshaft Position (CMP) signal
• Air Conditioning (A/C) Clutch
• Mass Air Flow (MAF)
• Manifold Absolute Pressure and Temperature (MAP-T) sensor
• Engine Coolant Temperature (ECT)
• Cylinder Head Temperature (CHT)
• Vehicle Speed Sensor (VSS) signal
• Boost Pressure Sensor
• Cam-Crank Phasing Sensor
• Keep Alive Memory (KAM)
• High pressure fuel injection pump
• Exhaust gas recirculation (EGR) valve lift potentiometer
• Fuel injectors
• Turbocharger
• Combustion noise monitor
• Barometric pressure sensor

Combustion Noise Monitor (Vehicles with common rail fuel injection)

In diesel variants, the Combustion Noise Monitor is used to trim the fuel injection pulse lengths. Each fuel injector has an associated set of correction data that is determined during a production end of line test. The Combustion Noise Monitor is used to determine how the fuel injector charateristic changes from this initial calibration over the life of the fuel injector.

EGR Monitor

The functionality of the EGR system is checked by comparing either the MAP sensor output or EGR lift potentiometer output (depending upon application) with expected values.

Turbocharger Boost Pressure Monitor (Vehicles with variable vane turbocharger)

The functionality of the turbocharger is determined by measuring the MAP sensor output under selected operating conditions. The output value is then compared with expected values.

Diagnostic Requirements

Vehicles equipped with EOBD, can be diagnosed using the Worldwide Diagnostic System (WDS). In order for the EOBD system to be invoked, a number of criteria must be met. Together these make up a drive cycle. After any repair, which could affect emissions, a dealer test cycle must be carried out on the vehicle, to make sure that engine management system operates correctly

Malfunction Indicator Lamp (MIL)

The MIL is located in the instrument cluster and is fitted to alert the driver to the fact that an abnormal condition has developed in the engine management system, that is having an adverse effect on emissions. In cases of misfires which are likely to cause catalytic converter damage, it flashes immediately. With all other faults it will illuminate continuously from the second trip after the condition occurred. Under normal operation it should illuminate at key-on and go out almost soon as the engine is started.

Diagnostic Trouble Codes

The diagnostic trouble codes (DTCs) given by the PCM are standardized, which means that generic scan tools can read results from all vehicles.

• The DTC is always a 5 digit alphanumerical code, for example ”P0100".
• The first digit of a code (letter) identifies the system which has set the code. Provision has been made for a total of four systems to be identified although only the 'P' code is required for EOBD.
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  'B' for the body
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  'C' for the chassis
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  'P' for the powertrain
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  'U' for the network communications systems
• All of the ”x0xxx" codes are standardized codes. However, any manufacturer can use additional codes over and above the standardized codes. These will be labelled ”x1xxx", "x2xxx" and so on.
• The third digit of a code (numeric) identifies the sub-system which has set the code.
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  'Px1xx' for metering of fuel and air supply
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  'Px2xx' for metering of fuel and air supply
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  'Px3xx' for ignition system – combustion misfires
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  'Px4xx' for auxiliary emission control equipment
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  'Px5xx' for vehicle speed, idle setting and other related inputs
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  'Px6xx' for trip computer and other related outputs
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  'Px7xx' for transmission.
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  'Px8xx' for transmission.
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  'Px9xx' category to be determined
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  'Px0xx' category to be determined
• When a concern occurs, the actions taken include storage of the relevant information and activation of the MIL occurs in line with the relevant legislation.

Inspection and Verification

Visual Inspection Chart