Electrical Diagrams
:1Air Bag (SRS):
WIRING DIAGRAM
Airbag: Component Location:
COMPONENT LOCATION VIEW
Airbag: Component ID:
COMPONENT ID
22A Main fuse board in the dashboard.
47T SRS warning lamp in the main instrument display panel.
331 Airbag control module under the centre console behind the handbrake.
333 Airbag.
336 Slip-ring contact (coil spring) in the steering wheel.
429 Bridging resistor, airbag, behind the glove box access panel.
445 Data link connector under the dash board adjacent to the steering
(H16-1) column.
540 Main instrument display panel on the dashboard.
545 Central warning lamp in main instrument display panel 2.
3-Pin Connector
H3-18 For slip-ring contact (coil spring) in the steering wheel.
Grounding Points
G4 Grounding point, centre console between the front seats.
DESCRIPTION OF OPERATION
Cars equipped with an airbag are marked SRS (Supplementary Restraint System) on the steering wheel centre pad and, if the car is also equipped with a passenger airbag, on top of the dashboard in front of the passenger.
The system consists of a control module located on the tunnel behind the centre console between the front seats, a steering wheel centre pad and in certain cases a passenger pad containing gas generators and airbags.
The system will be activated when a micro mechanical acceleration sensor in the control module senses a deceleration force.
Control Module 331
The control module incorporates a processor, safety sensor, energy reserves, voltage converter and a diagnostics unit.
The control module must be fitted so that it faces in the right direction.
Steering wheel centre pad (airbag module) 333 A
The steering wheel centre pad contains a gas generator and an airbag.
Gas Generator
The gas generator consists of an aluminum casing divided into a central chamber and two annular chambers.
The central chamber contains an electric detonator and an explosive charge connected with the inner annular chamber by means of passages.
The inner annular chamber contains fuel which on combustion generates a gas which passes through a filter in the outer annular chamber, connected to the inner chamber by passages, which purifies the gas before it continues out to the airbag.
Passenger Airbag 333B
The passenger safety restraint system (SRS) contains a gas generator and airbag.
Cars not equipped with a passenger airbag have bridging resistor 429 incorporated in connector H2-51 about 100 mm in front of the control module.
The connector is connected to pins 6 and 8 of the control module.
Gas Generator
The gas generator consists of an aluminium casing divided into an inner chamber, a centre chamber and two outer chambers.
The inner chamber contains an electric detonator and an explosive charge. Passages connect it with the centre chamber.
The centre chamber contains fuel pellets which on combustion generate a gas.
Passages fitted a filter connect the centre chamber with the two outer chambers. The filter separates particles from the gas.
In the outer chambers the gas passes through another filter before it reaches the airbag.
SRS Warning Lamp
The main instrument display panel contains two warning lamps. Both lamps light up as a system check when the ignition switch is turned to the Start or Drive position. If all systems are OK the lamp will go out after a few seconds.
In main instrument display panel 1 there are two bulbs (SRS 1 and SRS 2) behind the SRS symbol. When the system check is performed both bulbs light up for 3-4 seconds.
In main instrument display panel 2 there is one bulb (SRS 1) behind the SRS symbol and another bulb (SRS 2) for the central warning lamp. When the system check is performed, both bulbs light up for 3-4 seconds.
Power Supply
When the ignition switch is turned to the Start or Drive position, current is supplied via fuse 18 to pin 9 of the control module and to the SRS 1 bulb.
The control module starts an initial self-test for a maximum of 10 seconds. During this time the airbag cannot be triggered.
In the event of a collision, the energy reserves will serve as an extra power source and apply an igniting pulse to the electric detonators if the regular power supply has failed.
If the power fails for some other reason (such as a blown fuse), the SRS symbol lamp (main instrument display panel 1) or the SRS symbol and central warning lamp (main instrument display panel 2) will light up.
The central warning lamp is supplied with current from the main instrument display panel supply.
If the power supply has failed, the system will not be operative because the energy reserves are used up in only a few seconds.
Grounding
IMPORTANT: The ground cables of other systems must not be connected to the control module mounting screws as this may cause disturbances in the system and give rise to faulty indications from the diagnostics unit.
FAULT DIAGNOSIS HINTS
Before fault diagnosis is started:
^ Unplug the connector at the back of the steering wheel centre pad and passenger airbag.
^ Connect a reference resistor, part No. 84 71 153, to the appropriate connector.
Do not use instruments having their own power source, such as ohmmeters, diode testers and buzzers, when taking readings directly on the steering wheel centre pad or passenger airbag. Always disconnect the negative cable from the battery when any work is to be carried out on the system.
IMPORTANT:
A defective airbag component must not be repaired. Install a new component instead.
SRS cables must not be spliced.
Diagnostics unit
The diagnostics unit continuously monitors the air-bag system. Should the system develop a fault, the SRS symbol will flash for five minutes and then remain on without flashing.
On cars with a central warning lamp, the SRS symbol will flash for five minutes and then remain on without flashing and the central warning lamp will shine continuously.
After the unit has been activated (after it has sent a detonating pulse to the explosive charges in the gas generators), the SRS symbol will flash continuously.