2888293 - 5580C air bag system

This operation should only be carried out if an approved child's seat is installed on one of the two front passenger seats.

The system is connected to the:

• Diagnostic socket for checking the system with the Examiner or other diagnostic equipment
• Warning light in the instrument panel for signalling faults
• Passenger Air Bag disablement warning light on the instrument panel

When operations are carried out to the Air Bag system the recommended safety instructions must be followed precisely. For further details see REPAIR PROCEDURES  See assembly 5580C   air bag system

The system consists of the following components:

• electronic cotnrol unit
• driver Air Bag
• passenger Air Bag
• switch for disabling passenger Air Bag

Electronic cotnrol unit

Functions

In addition, this control unit has the following functions:

• Energy accumulation : the control unit is supplied with 12 V when the ignition is on, but can nevertheless continue operating for a few fractions of a second after the supply has been cut off. This is possible thanks to the presence of a buffer condenser which accumulates sufficient electrical energy to produce the Air Bag activating signal. The operation of the system is therefore guaranteed even if the impact causes a fall in the system voltage (e.g. battery damaged or broken, break in the supply cables, etc.).
• Check attachment : the control logic also checks the electrical contact between the control unit casing and the bodywork, thus ensuring a rigid connection to the body shell.
• Fa ilure m emory: whilst the vehicle is running, the electronic continuously carries out the system fault diagnosis, checking the continuity of the circuits and components. If a fault is detected it is memorized and the "Air Bag failure" warning light in the instrument panel comes on at the same time. The failure memory can be consulted by connecting the diagnostic equipment (Examiner or S.D.C.) to the diagnostic socket, as described below.
• Crash memory: the control unit microprocessor carries out complex calculation algorhythms for the signal coming from the accelerometer sensor and determines the severity of the impact. According to the severity and, with the go ahead of the safety sensor, it sends a signal to activate the Air Bags. This activation order is stored in a special crash memory which contains information relating to the exceeding of the intervention thresholds and the go-ahead for the safety sensor.
• Wiring recognition : the control unit can recognize the type of system installed: complete system or reduced system without passenger Air Bag. This takes place via a specific recognition pin on the control unit: pin 30 earthed means passenger's Air Bag present, while pin 30 open means passenger's Air Bag absent.

Location

Control unit pin-out

Pin, Signal 1, Activation (-) of driver's Air Bag 2, Driver's Air Bag activation (+) 3, Passenger Air Bag activation - internal generator 4, Passenger Air Bag activation (+) - internal generator 5, Passenger Air Bag disabling device (-) 6, (N.C.) 7, (N.C.) 8, Passenger Air Bag disablement device (+) 9, Diagnostic serial line K 10, (N.C.) 11, (N.C.) 12, Crash output (N.C.) 13, Passenger Air Bag activation (+) - external generator 14, Passenger Air Bag activation (-) - external generator 15, Supply controlled by the ignition 16, Driver's Air Bag D.C. bar 17, Driver's Air Bag D.D. bar 18, Passenger Air Bag D.C. bar - external generator 19, Passenger Air Bag D.C. bar - external generator 20, Passenger Air Bag disabling warning light signal 21, D.C. bar 22, D.C. bar 23, Air Bag system failure warning light signal 24, Earth 25, D.C. bar 26, D.C. bar 27, Passenger presence sensor signal (N.C.) 28, Passenger Air Bag D.C. bar - internal generator 29, Passenger Air Bag D.C. bar - internal generator 30, wiring recognition signal (version with passenger Air Bag)

Driver's Air Bag

The Air Bag is a passive safety device made up of a bag which, in the case of a frontal impact, automatically inflates placing itself between the bodies of the vehicle occupants and the structure of the front part of the passenger compartment.The driver's Air Bag module is located in the centre of the steering wheel; it is fitted on a rocker plate which allows the operation of the horns.The plate, fixed to the steering wheel by two bolts, houses the folded bag and gas generator device.The gas generator is of a new "ecological" design: the gases which are released are neither toxic nor irritant.The electrical connector of the gas generator adopts a particular safety device: a stop lug only closes when the connector has been inserted correctly, and it deactivates a short circuit clip inside the connector which prevents any possibility of accidental activation of the module.

1, Steering wheel 2, Gas generator 3, Rocker plate 4, Folded bag 5, Cover

Operation

The generator can be electrically activated by a signal coming from the electronic control unit.Thus a "tablet" of pyrotechnic substance is primed, which causes the expansion of a small quantity of primer gas, which in turn causes a larger quantity of pyrotechnic material, located in an outer circular ring, to react. This "NON AZIDE" material (i.e. with no sodium nitride) produces a gas (mainly nitrogen) which emerges from the special holes and expands in the bag, whose total capacity is about 42 litres.After being inflated by the gas, the bag deflates immediately through the suitably calibrated holes on the rear.The module plastic cover opens upwards along the pre-determined breakage lines which allow the bag to come out completely.

1, Electrical connection 2, Pyrotechnic charge 3, Deflation holes 4, Gas generator 5, Bag inflation holes

Clock spring

A clock spring device allows the Air Bag module connecting cables, fitted in the steering wheel, to follow the rotation of the latter without danger of breaking.This device is fitted on the steering column switch unit and consists of two plates, the lower one fixed to the steering column switch unit and the upper wheel fixed to the steering wheel.The module connecting cables and the horn buttons are wound around inside the two plates allowing them to follow the movement of the steering wheel.

1, Clock spring 2, Air Bag electrical connection 3, Horn electrical connection 4, Safety deviceAn internal safety device automatically locks the rotation of the two plates when the steering wheel is removed from the clock spring. This prevents the top plate, no longer attached to the steering wheel, from rotating freely and so winding or unwinding the clock spring which might then break. The new device is supplied with a safety key.

Passenger Air Bag

The passenger Air Bag module is located on the facia, and it protects the two front passengers.It is a module which consists of two gas generators which inflate a single large bag (120 litres) of a suitable shape to protect the occupants of the central and side seats. This absolutely innovative solution provides optimum protection for both occupants. The composition and operation are the same as the driver's Air Bag, but with two gas generators, of the same type as that installed in the steering wheel.The passenger module is fixed directly to the vehicle crossmember by a special bracket.A linen-faced cover contains the folded bag, but does not prevent it from emerging in the case of activation.

1, Vehicle crossmember 2, Passenger Air Bag module 3, Bag cover 4, Gas generators 5, Electrical connections

Module flap

A plastic flap whichis integrated in the dashboard allows the bag to come out correctly when it inflates.It is connected to the dashboard by means of four metal pins.It is also fixed to the crossmember by two retaining belts which, in the case of activation of the Air Bag, allow the flap to rotate and retain it.In the case of intervention of the Air Bag, the flap opens upwards, thereby allowing the bag to come out completely and correctly.

1, Fixing pins 2, Retaining belts 3, Flap Inside the control unit, there is an accelerometric sensor whose signal, suitably processed by a microprocessor, makes it possible to determine the severity of an impact and consequently to decide whether or not to activate the Air Bags. A second sensor with safety functions gives the enablement for activation of the Air Bags.The control unit detects frontal collisions, or those within a certain angle of impact.In the case of side or rear-end impacts (shunts) or the vehicle overturning, if the system is not activated, this does not mean there is a malfunction.

System self-test

The control unit carries out a continuous self-test of the system's operation.

In particular:

• it detects and memorizes any faults
• it recognizes the various components and the type of fault
• it signals the onset of these faults via the special warning light in the instrument panel.

If a fault is detected with the manual disabling switch, it is considered in the OFF state and therefore the operation of the passenger Air Bag is inhibited.The faults stored in the control unit memory can be cancelled, after the fault has been repaired, using the Examiner or other diagnostic equipment.System activations following a particularly serious impact are memorized by the control unit.In the case of an impact which has cause the system to be activated, the control unit memory cannot be cancelled, so the control unit must always be replaced.

"air bag system failure signal" warning light

During starting (key in ON position), the red coloured "Air Bag failure" warning light comes on for about 4 seconds (initial self-test stage) and then goes out.

The warning light remains on or comes on, during the normal operation of the vehicle, in the following cases:

• the control unit detects a fault in the Air Bag system
• the control unit detects an impact with activation of the system
• the control unit detects a fault in the actual warning light connection circuit.

If the control unit detects fault, it can, in certain cases, disable the system: therefore it is suggested that the User go to the closest Service Centre as soon as possible to have the fault repaired because the system is no longer capable of working properly.Once the fault is signalled, the warning light remains on until the fault is repaired or cancelled from the errors memory using the Examiner or other diagnostic equipment.

Passenger Air Bag disabling

The activation of the passenger Air Bag can be excluded voluntarily by the control unit by means of a switch operated by the car key, which is located on the facia, inside the closed glove compartment, opposite the driverThis device must only be used if a child is seated at the front, on a proper child seat, which is rear facing; the switch must be set to OFF.In this case, the control unit excludes the activation of the passenger's Air Bag and also switches on the "passenger Air Bag disablement" warning light on the instrument panel.

In thiis condition, any passenger occupying the remaining front seat will be protected solely by the seat belt with pretensioner. THE SAFEST PLACE FOR AN APPROVED CHILD SEAT IS ON THE REAR SEATS.

Do not operate the device when the ignition is on (e.g. using the second key): in this case the control unit would memorize an error, and the "Air Bag failure" warning light would come on.

1, Switch with key 2, OFF Position : Passenger Air Bag disabled 3, ON Position : Passenger Air Bag enabled

"passenger air bag disabled" warning light

During starting (key set to ON position) the orange coloured "passenger Air Bag disabled" warning light comes on for about 4 seconds.- if the key for the manual disabling of the passenger Air Bag is switched OFF, the warning light remains on.- if, on the other hand, the key is switched ON, the warning light flashes for a further 4 seconds and then goes out.