AIR BAG SYSTEM

Description 5580C

PASSIVE SAFETY SYSTEM

The vehicle is equipped with an electronic control system that governs the activation of specific containment devices in the event of frontal or side impact:

The frontal protection system includes:

- dual activation stage driver''s front Air Bag;

- front passenger Air Bag;

- driver''s kneebag (optional);

- front seat belts with pretensioner and load limiter;

- rear seat belts with pretensioner and load limiter (optional);

- additional front impact detection sensor;

The side protection system comprises:

- two Side Bags housed in the front seats (optional);

- two drop-down headbags housed in the under-roof rails (optional);

- two impact detection sensors located in the central pillar (optional).

The dual stage driver''s front air bag is capable of automatically adapting the activation parameters depending on the seriousness of the impact:

- when the impact is of moderate severity, the electronic control unit controls the first air bag activation stage so that the energy discharged onto the occupant is not harmful;

- for very severe crashes, the control unit activates the first and second stage with a very slight delay in order to absorb the occupant''s greater kinetic energy before he strikes the steering wheel.

- for medium severity impacts the second stage is also activated after a preset time to ensure the charge is used fully.

- an early crash sensor, located on the front crossmeber near the bonnet lock, helps the electronic control unit to anticipate the intervention of all the front air bags.

The Air Bag system components are designed to work on a specific vehicle. They therefore CANNOT be tampered with, adapted or installed on other types of vehicle.

For safety reasons, NO continuity checks can be carried out on the wiring.

The electrical connection between the airbag system components is via dedicated wiring integral with the dashboard cable loom and the rear cable loom.

The control unit is connected to the system via two connectors, one for the dashboard lead and the other for the rear lead.

The control unit is connected to the vehicle CAN network via which it exchanges information with the other nodes, turns on the instrument panel warning lights and carries out diagnostic operations.

Because the control unit is a node in the CAN, the airbag system is connected:

- the standard diagnostic socket via the CAN

- to the instrument panel, again via the CAN, to control the airbag system failure, seat belt unfastened and passenger airbag deactivated warning lights in addition to the belt unfastened buzzer.

- to the Body Computer for potential end of line customisation (Proxy) with a consequent reduction in the number of spare parts.

If the vehicle is equipped with side bags, deactivation of the front passenger side air bag module also disables the side bag.

COMPOSITION

The system consists of the following devices:

- an electronic control unit;

- dual driver and passenger front air bags with dual-stage activation and passenger air bag with single stage activation

- driver''s kneebag with single stage activation;

- a supplementary impact detection sensor, the ECS (Early Crash Sensor);

- two Side Bags on the front seats;

- two window bag modules for the side protection of occupants;

- two side impact sensors in the side pillars;

- four electronic pretensioners on the seat belts.

The following indications show the system is working properly:

- system fault warning light (red) in the instrument panel:

- passenger air bag disabled warning light on the instrument panel;

- front seat belt unfastened warning light on the instrument panel;

- connection viai the B-CAN with the diagnostic socket - for function checks using an EXAMINER.

1 - Electronic control unit

2 - Passenger side airbag module

3 - Driver side airbag module

4 - Passenger Side Bag module

5 - Passenger side impact sensor

6 - Passenger window bag module

7 - Driver side window bag module

8 - Driver side impact sensor

9 - Driver''s side front pretensioner

10 - Front passenger side pretensioner

11 - Driver''s side bag module

12 - Driver''s air bag module

13 - Frontal impact sensor

14 - Driver''s side rear pretensioner

15 - Rear passenger side pretensioner

16 - Air Bag system fault indication warning light

17 - Passenger side air bag deactivation warning light

18 - Seat belt not fastened warning light

ELECTRONIC CONTROL UNIT

The following diagram shows the control unit.

1 - Electronic control unit

2 - Indication showing direction of motion

The control unit represents the occupant protection system central processing unit and is secured rigidly to the vehicle floor pane near the central tunnel. It manages all the containment system detection and activation devices by processing signals from the various sensors distributed throughout the vehicle and internal sensors.

If the control unit falls to the ground or is subject to abnormal knocks during handling, it MUST be replaced.

Composition

The control unit has an electronic deceleration sensor which, with the assistance of front and side satellite sensors and, via a dedicated calculation algorithm, manages the activation of the front and side modules and the pretensioners.

Operation

Frontal impact:

When the impact is of moderate severity, the electronic control unit controls the first air bag activation stage for the driver''s air bag so that the energy discharged onto the occupant is not harmful.

Conversely, in the case of very severe impact, the control unit activates both stages almost simultaneously to absorb most of the kinetic energy from the occupant''s body before it strikes the steering wheel or dashboard.

Side impact:

Similarly, when side impact occurs, the control unit is able to recognise direction and intensity and thus activate both air bags and the pretensioners present on the side affected by impact. To provide total cover against side impacts, two satellite sensors located in the centre pillars are used.

When there is a side impact, the satellite sensors detect the deceleration due to the impact and notify the control unit which, by means of a dedicated calculation algorithm, manages the activation of the side modules and the pretensioners.

The side air bags (window bags and Side Bags) are activated simultaneously and independently of the front safety devices.

After each activation of one of the controlled systems (pretensioners, front airbags, sidebags), the control unit stores the activation in its permanent memory and controls activation of the fault warning light on the instrument panel.

Before it is replaced, the control unit guarantees individual device activation for a maximum number of:

- 3 impacts with activation of the seat belt pretensioners alone;

- 3 impacts in total (right or left) with side bag activation;

- 1 impact with activation of the pretensioners and front airbags;

- any combination of the above cases up to the maximum number.

If one of the limits described is not reached, it will be possible to reuse the control unit after carrying out the RESET procedure using the EXAMINER once system operating conditions have been restored. The final activation, corresponding to the maximum number for the limits indicated above, will prevent further reset procedures.

Control unit pin out

CONNECTOR A (dashboard wiring, BLUE)

CONNECTOR B (rear wiring)

- version without side bags (BLACK connector).

CONNECTOR B (rear wiring)

- extensive version with side bags (GREY connector).

Self-diagnosis

The control unit carries out continuous self-diagnosis of system operation. Specifically:

- it detects and stores faults;

- it diagnoses connnections to system components and any type of fault that has occurred;

- it indicates the source of these faults by turning on an instrument panel warning light.

Faults stored in the control unit may be deleted only after the fault has been repaired by means of the EXAMINER device.

If the fault is due to an error inside the control unit it should be replaced.

DRIVER''S AIR BAG MODULE

Specifications

The driver''s air bag is a passive safety device. It takes the form of a bag that inflates automatically in the case of frontal impact to interpose itself between the driver''s body and front passenger compartment structures. The Air Bag module is installed in the middle of the steering wheel. The module cover also acts as a horn control.

Composition

The module comprises:

- a plastic cover that tears at preset points when activated to allow the bag to expand correctly.

- a 60 litre bag, made out of nylon thread woven to minimse skin abrasions in the case of contact and folded in such a way as to ensure that inflation is gradual and not directed toward the driver;

- a pyrotechnic type gas generator;

- a plastic housing;

- the control device from the horns.

Operation

Bag inflation is determined by a gas generator that offers two intervention stages that can be activated separately according to impact severity.

The gas generator is activated by two electrical resistances that burn propellant inside the generator to allow the bag to expand.

When fully inflated, the bag is in an optimal position to protect the occupant. Bag deflation is immediate, due to two holes present in the lower part of the bag. This holes also soften contact between passenger and bag to avoid the risk of abrasions.

CLOCK SPRING

The following figure shows the clock spring.

1 - Electrical connection for connecting air bag first stage

2 - Electrical connection for connecting air bag second stage

3 - Steering wheel electric functions connection (horns and radio controls)

4 - Clock spring

Specifications

The clock spring transfers the electrical signal to controls on the steering wheel (horn and other optional controls) and connects the airbag module without risk of breakage.

The device consists of two plates and is built into the stalk unit via its lower plate. It is secured in place by means of fasteners on the upper plate. Inside the two plates, the leads connecting the module and horn buttons are wound in a coil so that they can follow steering wheel movements.

Composition

The clock spring is fitted with three leads on the steering wheel side. Two of these are used to connect the air bag module (first and second stage) and one to connect the steering wheel electrical functions (horn, radio controls).

A ring on the upper plate, steering wheel side, automatically prevents the two plates turning in relation to one another when the device is detached from the steering wheel. New devices are fitted with a safety key for transport, to be removed after installation.

Operation

Inside the two plates, the leads connecting the air bag module and the various electrical functions are wound into a spiral with sufficient coils to follow the steering wheel rotations.

The upper plate is turned by fasteners on the inside of the retaining ring that fit into the seat on the steering wheel hub. In a working position, the steering wheel presses on the ring to release it from its fasteners and thus allow both plates to turn freely.

When the steering wheel is removed, the spring-loaded ring locks rotation between both plates. This function prevents the upper plate, now no longer secured to the steering wheel, from turning freely and unwinding or winding the coil inside the device and possibly causing it to break.

The following must be observed during operations that require removal of the steering wheel and device.

- always work with the car''s wheels aligned straight ahead;

- secure both plates with a band for safety before removing the device from the steering wheel stalk unit.

If the clock spring is being reused, it is advisable to secure the two shims with a band to prevent accidental rotation.

If the upper plate should turn in relation to the lower plate for any reason so that the exact starting position is no longer certain, the clock spring MUST be replaced.

PASSENGER AIR BAG MODULE

Specifications

The passenger airbag module is a passive safety device that protects the front passenger in the event of front impact by means of a bag that interposes itself between the occupant and the vehicle dashboard.

Composition

The module comprises:

- a plastic housing;

- a 120 litre bag in nylon, a fabric that minimises skin abrasions in the event of contact. The bag is folded so that it does not inflate directly towards the occupant.

- a pyrotechnic type gas generator.

Operation

The gas generator is electrically activated by means of a signal from the electronic control module. Following this signal, a pyrotechnic activation is triggered that causes the gas in the generator to expand.

Bag inflation opens the flap in the dashboard along predefined cut lines. When fully inflated, the bag is in an optimal position to protect the occupant.

The braids inside the airbag unfold in such a way as to allow inflation to the maximum specified dimensions to prevent collateral damaging effects on passengers.

Passenger air bag module disablement

The user can deactivate the passenger bag in order to install a child seat without any risk. When fitted in the front, it should be installed facing away from the direction of motion.

This function is activated by means of the setup menu on the instrument panel as follows:

- with the vehicle parked, press the MODE pushbutton to gain access to the setup menu;

- select the "Passenger bag" function by means of the + or - pushbuttons;

- press the MODE button and, using the + or - buttons, select the "Passenger bag: Off) message (for deactivation) or the message (Passenger bag: On message (for activation); lastly, press the MODE button again to confirm.

When the function is on, the instrument panel warning light stays on.

KNEE AIR BAG MODULE

Specifications

An optional airbag module is also supplied as an option. This is fitted in the lower part of the facia in front of the driver''s knees. This module, in addition to protecting the lower limbs, increases protection for the driver, particularly by preventing them from sliding forward, which is a possible cause of injury to the legs and chest.

Composition

The knee bag module consists of:

- a metal container;

- a gas generator;

- a nylon bag;

- a plastic cover.

The container is secured to a mounting plate and a safety plate that secures it rigidly to the lower part of the dashboard.

The plastic cover tears at preset points when activated to allow the bag to expand correctly.

Operation

The gas generator is electrically activated by means of a signal from the electronic control module. Following this signal, a pyrotechnic activation is triggered that causes the gas in the generator to expand. The expanding gases emerge through openings to inflate the bag. When the bag is inflated, the bag is in an optimum position to perform its role of protecting the occupant.

SIDE BAG MODULE

Specifications

The front seats contain two side bag modules to increase the protection offered by the body in the event of side impact.

This device ensures the airbag is always in an optimum position in relation to the occupant, regardless of the angle of the seat or the size of the occupant.

The side bag protects the chest and pelvis areas and also - together with the door panels - protects critical areas of the body such as the ribs and abdomen.

Its position on the seat always ensures maximum efficacy irrespective of seat position, even if the seat occupant is not seated correctly, because bag opening dynamics minimise the risk of body damage due to impact against the body.

Do not cover the front seat backrest with extra covers.

Do not wash the seat backrest with water or steam under pressure.

Composition

The side bag module consists of:

- a metal container;

- a gas generator;

- a nylon bag with a volume of around 12 litres;

- a plastic cover.

The plastic cover tears at preset points when activated to allow the bag to expand correctly.

The module is connected to the electrical system by means of two leads with yellow sheaths. These are contained, together with the seat earth connection lead, in a protective fabric-lined duct secured to the seat structure.

Operation

The gas generator is electrically activated by means of a signal from the electronic control module. Following this signal, a pyrotechnic activation is triggered that causes the gas in the generator to expand. The gases expand and emerge through openings to inflate the bag. Bag inflation causes the weak seams in the backrest trim to yield and allow the bag to emerge.

When fully inflated, the bag is in an optimal position to protect the occupant.

WINDOW BAG MODULE

Specifications

The window bags are activated together with the sidebags and interpose themselves between the occupant and the vehicle to prevent the head coming into contact with highly intrusive objects such as glass, pillars etc.

Because the window bags extend from the front pillar to the luggage compartment, they protect front and rear passengers. The window bag system offers the best performance due to the broad area covered and their ability to be self-supporting even without a backing.

Composition

The window bag module consists of:

- a gas generator secured by two bracket to the rear pillar;

- a metal connecting pipe between the gas generator and the bag;

- a bag with a volume of about 30 litres made from a permeable nylon fabric folded inside a container. The bag is designed to ensure, once fully inflated, correct absorption of impact energy while maintaining the occupants'' heads at a proper distance from the impact area. Once fully inflated, the gas leaves the bag immediately through the porous tissue.

- plastic clips that secure the bag to the ceiling rail;

- plastic plates to secure the bag onto the vehicle;

- a retaining strap secured to the front pillar that holds the bag in position once inflated;

Operation

The gas generator is electrically activated by means of a signal from the electronic control module. Following this signal, a pyrotechnic activation is triggered that causes the gas in the generator to expand.

On expanding the gases escape via special openings and are evenly distributed along the entire bag.

The increase in bag volume causes the sleeve seams to yield and the trim to open. Everything is arranged so that the bag emerges correctly downward.

The bag is made to inflate correctly by a retaining strap on the front end of the bag.

When fully inflated, the bag is in an optimal position to protect the occupant.

The bag deflates immediately after being inflated by the gas because the fabric is permeable.

FRONT IMPACT SATELLITE SENSOR

SIDE IMPACT SATELLITE SENSORS

SEAT BELT PRETENSIONERS

Specifications

The pretensioners are pyrotechnic devices that are activated electrically by means of a signal from the electronic control unit. They are built into the reel of the front and rear seat belts. Activation of the seat belt pretensioners is controlled by the same strategy as the air bags.

The pretensioners are designed to take up slack in the seat belt to ensure it holds the occupant against the backrest from the first moments of impact, thus reducing movement inside the passenger compartment.

The seat belts are also fitted with load limiters which decrease the force transmitted by the belts to the chest: the force level at which the limiters act is sufficient to considerably reduce the risk of fracturing shoulder blades and ribs, even in people with brittle bones (e.g. the elderly).

Operation

The following figure shows the pretensioner mechanism.

1 - Gas generator

2 - Electrical connector

3 - Tape

4 - Reel

When the car decelerates to a sufficient extent, as measured by system acceleromters, the electronic sensor in the electronic control unit sends a signal to trigger the gas generator pyrotechnic charges. The combustion of the propellant produces a chemical reaction creating inert gas whose pressure produces a force that thrusts a piston upwards, changing the rotary movement of the reel into the opposite direction of the seat belt, rewinding it by a few centimetres.

Once the pretensioners have been activated, the belts are locked and must be replaced.

AIRBAG SYSTEM WARNING LIGHTS

1 - Air Bag system fault warning light

2 - Passenger side disablement warning light

3 - Seat belt not fastened warning light

Air bag system fault warning light

At key on, the fault warning light (red) comes on for about four seconds (initial self-diagnosis stage) and then goes off.

If no system faults are detected at key on and no fault conditions are present in the fault memory, the warning light goes off after four seconds of self-diagnosis. Otherwise it stays on.

The warning light stays or comes on during normal car operation in the following cases:

- the control unit detects a fault in the airbag system;

- the control unit detects a crash with system activation.

As a consequence of a crash when the pretensioners or sidebags alone are activated, the warning light stays on until system operating conditions are restored (replacement of affected part or control unit repair using an EXAMINER)

If the crash causes the front airbag modules to activate, the warning light stays on permanently because the control unit cannot reset (in this case the control unit must be replaced).

If internal operating errors occur during the operational lifetime of the control unit that cannot be repaired by means of the EXAMINER, these are indicated by permanent activation of the warning light.

Passenger air bag disabled warning light

At the key ON, the yellow passenger side air bag disabled warning light comes on for about four seconds (initial self-diagnosis stage).

The passgner Air Bag warning light flashes if the control unit detects a fault in the Air Bag system failure warning light.

Seat belt reminder

"first warning cycle": signalling via warning light

The "seat belts" warning light signals that the seat belt is not fastened (driver''s or passenger side) coming on constantly from the Key ON.

"warning cycle": indication via warning light and buzzer

The warning light starts to flash and the buzzer sounds continuously for 6 secs and then intermittently for 90 secs if one of the following conditions is verified:

- Time elapsed 50 secs and vehicle speed above 10 km/h

- Vehicle speed above 20 km/h

- Distance travelled more than 400 m

If the seat belts are fastened during the cycle, the warning cycle is automatically interrupted and is only repeated if the seat belt not fastened condition is detected once again. The cycle is also interrupted when reverse gear is engaged (the warning light only remains on constantly) and is only repeated when the seat belt not fastened condition is detected once again and the vehicle speed exceeds 10 km/h.

Warning cycle exclusion mode

The driver can temporarily deactivate the warning cycle (the warning is activated again if there is a Key-OFF of more than 1 minute) by fastening the front seat belt(s) before the Key ON, holding it (them) for at least 20 secs with the key ON and undoing it (them) within 1 minute of the key-on.

The user can deactivate the warning cycle permanently only with the aid of the Technical Service dept.

The deactivation procedure must be performed using a diagnostic instrument (Examiner) in communication with the control panel.

Noone can deactivate the signal issued by the warning light on the dashboard. This is always present (fixed light) if the seat belt is unfastened.

Warning cycle reactivation method

The driver can reactivate the warning cycle (if it is permanently deactivated) through intervention from the Aftersales Service Department or through a special item in the set up menu. This item disappears once the warning cycle is reactivated.