3232972 - 5580C air bag system

The car may be fitted with an electronically-controlled safety system that sets off the front seat belt pretensioners and the driver's air bag, passenger air bag and sidebags in the case of frontal and/or side impact of a certain severity.

The passenger Air Bag can be deactivated:

• manually, by means of a special switch,
• automatically by a sensor located in the seat (only up to 5/99).

The system consists of the following components:

• Electronic cotnrol unit
• driver Air Bag
• Passenger side air bag
• Left belt pretensioner
• Right belt pretensioner
• switch for disabling passenger Air Bag
• Sensor for automatically disabling passenger side Air Bag (only up to 5/99)

The system is connected with the:

• Diagnostic socket for checking the system with the Examiner or other diagnostic equipment
• Warning light in the instrument panel for signalling faults
• Warning light in the instrument panel for indicating passenger Air Bag disabled.

The system components are interconnected and are connected to the rest of the electrical equipment by means of special wiring which can be easily recognized as it has a yellow coloured outer casing.

there are two possible configurations for the system.

• the standard configuration, fitted as standard, where there is a driver's Air Bag and two pretensioners.
• the complete configuration, which is optional and where there is also a passenger Air Bag and disabling devices.

Warning: carefully observe the safety regulations when working on the Air Bag system. For further details see PROCEDURES 5580C

System components

Refer to the illustration 1, Electronic control unit 2, Driver's Air Bag 3, Passenger Air Bag 4, Left seat belt pretensioner 5, Right seat belt pretensioner 6, Switch disabling passenger Air Bag 7, Passenger air bag automatic disablement sensor 8, Diagnostic socket for checking the system 9, Warning light in the instrument panel for signalling faults 10, Warning light in the instrument panel for signalling passenger Air Bag disabling

Electronic cotnrol unit

An electronic control unit manages the entire system by controlling all the components and activating the restraint systems (pretensioners and airbags) as necessary.

Operation

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 has two different intervention levels:

• at the first level only the pretensioners are activated
• the second level operates both airbags and pretensioners.

The control unit only detects frontal impacts. In the case of side impacts, collisions or the vehicle overturning, it does not activate the system.

Control unit specifications

- Energy accumulation: the control unit receives a 12 V supply with the ignition in the ON position, but it still operates for a further 220 msec approx after the supply is 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.).- Fixing check: the control logic also checks the electrical contact between the control unit casing and the bodywork, thus ensuring a rigid connection to the bodyshell.- Failure memory: 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's microprocessor carries out complex calculation and check algorithms on the signal coming from the accelerometer sensor, and determines the severity of a crash. 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 with 4 modules (2 Air Bags and 2 pretensioners) 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.

Control unit pin-out

Refer to the illustration 30-way connector 1, Driver's Air Bag activation (-) 2, Driver's Air Bag activation (+) 3, Passenger Air Bag activation (-) 4, Passenger Air Bag activation (+) 5, Passenger Air Bag disabling device (-) 6, Passenger pretensioner activation (+) 7, Passenger pretensioner activation (-) 8, Earth for fault diagnosis (Not connected) 9, Diagnostic line K 10, Driver's pretensioner activation (+) 11, Driver's pretensioner activation (-) 12, Crash output (N.C.) 13, Air Bag system failure warning light signal 14, Earth 15, Supply controlled by the ignition 16, Driver's Air Bag S.C. 17, Driver's airbag S.C. 18, Passenger airbag S.C. 19, Passenger airbag S.C. 20, Passenger Air Bag disabling warning light signal 21, Passenger side pretensioner S.C. 22, Passenger side pretensioner S.C. 23, Passenger presence sensor signal (up to 11/99) 24, Passenger Air Bag disabling device (+) 25, Driver side pretensioner S.C. 26, Driver side pretensioner S.C. 27, Passenger presence sensor signal (up to 11/99) 28, Failure warning light S.C. 29, Earth S.C. 30, Wiring recognition signal For further details see wiring diagram, function  See E7030  AIRBAG

Driver 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 tilting plate which enables the horn to be operated.The plate, fixed to the steering wheel by two bolts, houses the metal container with the folded bag and the gas generator device. 1, Cover 2, Metal container 3, Folded bag 4, Gas generator The gas generator can be electrically activated by a signal coming from the electronic control unit.A propellent charge is then triggered, which releases a compressed gas (Argon) which expands in the bag which has a total capacity of around 45 litres.The bag deflates immediately after it has been inflated, thanks to the permeable nature of the material from which it is made.The module plastic cover opens upwards along the pre-determined breakage lines which allow the bag to come out completely. 1, Compressed argon 2, Propellant charge 3, Inflation openings 4, Electrical primer 5, Electrical connection

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, Safety springs 3, Air Bag electrical connection 4, Horn electrical connection

A safety device, consisting of two springs, 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.When refitting the steering wheel, the device automatically unlocks.If, for any reaon, the upper plate rotates in relation to the lower one and its original position prior to removal can no longer be identified, it is essential to replace the clock spring. For further details see op   5580C12  clock spring for air bag module on steering wheel r rT2 Passenger Side Air BagThe passenger airbag is located on the facia, above the glove compartment.The composition and operation are the same as the driver's Air Bag, except for the dimensions of the bag which is larger: about 90 litres.The passenger module is fixed directly to the vehicle crossmember by a special bracket. 1, Vehicle crossmember 2, Passenger Air Bag module 3, Electrical connection

Module flap

A padded flap which is integrated in the dashboard allows the bag to come out correctly when it inflates.It is connected to the actual dashboard by means of two hooks and two springs with a pre-set yield point. It is also fixed to the crossmember by a bracket and three retaining belts, which prevent the inflation of the bag detaching the flap from the dashboard.In the case of the intervention of the Air Bag, the flap opens upwards, breaking the two springs, thereby allowing the bag to come out completely and correctly.

The flap can only be removed from the dashboard by breaking the prings which must, in that case, be replaced.

1, Retaining hooks 2, Retaining belts 3, Flap 4, Clips with pre-established break point

Passenger air bag disablement

There are two methods for excluding the activation of the passenger Air Bag by the control unit:

• manual: using the key
• automatic: through a special sensor on the seat (present up to 5/99).

The manual intervention voluntarily and temporarily excludes the operation of the passenger Air Bag.The automatic intervention prevents the intervention of the passenger Air Bag if the front seat is empty, in order to reduce vehicle repair costs following the passenger Air Bag being activated unnecessarily.Passenger airbag manual disablement switchA switch which can be operated by the vehicle key allows the passenger Air Bag to be enabled (ON) or disabled (OFF). It is positioned at the edge of the dashboard, passenger side, and is only accessible with the door open.In this case, the control unit excludes the activation of the passenger Air Bag, but enables the operation of the pretensioner: this is because if a passenger is present, but the switch has been incorrectly turned OFF, the Air Bag does not intervene, but at least the pretensioner does.When the key is turned to OFF, the control unit also controls the activation of a passenger air bag disablement warning light on the instrument panel. 1, Switch with key 2, OFF Position: Passenger Air Bag disabled 3, ON Position: Passenger Air Bag enabled Automatic passenger air bag disablement sensor (present up to 5/99).A sensor for detecting the presence of a passenger is fitted in the seat, between the upholstery and the covering: it consists of numerous cells distributed throughout part of the seat which is "sat on" (the flat centre section).The sensor is the resistive type, made up of electrical resistances which vary with the pressure applied.The control unit "reads" the sensor resistance, detecting whether or not a passenger is present.When it detects the "no passenger present" condition constantly for at least 30 seconds, the control unit excludes the operation of the passenger Air Bag and the pretensioner.If the sensor then detects the "passenger present" condition, the control unit immediately reactivates the passenger Air Bag, and the pretensioner.If there is a change from the "not present" condition to the "passenger present" condition with the ignition switch in the ON position, the control unit makes the "passenger Air Bag disabled" warning light in the instrument panel flash for 4 seconds.This does not take place in the reverse situation (change from "present" to "not present").

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