Initial Inspection and Diagnostic Overview
General information
The airbag system is monitored continuously by a diagnosis unit located in the triggering unit. Any faults present are highlighted by a warning lamp.
If a fault occurs, the central warning lamp and the airbag system warning lamp come on.
The airbag warning lamp lights for approx. 5 seconds after the ignition is switched on and will go off if no fault is stored in the fault memory.
If the lamp comes on again, this means that a fault is present in the system. The fault may be read out with System Tester 9288. If the fault is not crash-relevant, the warning lamp is not activated all the time but only for approx. 2 minutes.
Note: To allow the triggering unit to recognize all faults in the system, it requires a minimum time span of 10 seconds to ensure that allow potential fault sources are checked during the vehicle test, the ignition must be switched on for at least 10 seconds.
The fault memory must be erased after a fault that has occurred in the airbag system has been removed.
Replacement of a component should be recorded in the Warranty and Maintenance booklet. Glue the documentation number into the space provided. The documentation number is indicated on a tear-off sticker on the spare part.
The following components must be removed and replaced if the vehicle has been involved in an accident that has caused the airbag to be triggered:
- Contact unit
- Both airbag units.
Operation of individual components
1. Triggering unit
Processes the incoming signals and triggers the airbag system when an accident situation is detected (also refer to system description).
2. Passenger airbag unit
Includes airbag and gas generator for the passenger.
3. Warning lamp
1. Displays system readiness.
2. Displays a fault.
4 Driver airbag unit
Includes airbag and gas generator for the driver.
5. Contact unit
Provides connection between triggering unit and driver airbag unit.
System description
The airbag system consists of the following components: triggering unit, contact unit, driver airbag unit, passenger airbag unit and warning lamp. A self-test is run after the ignition is switched on. The warning lamp is activated during the self-test. If no faults are stored in the fault memory, the warning lamp will go out after approx. 5 seconds.
A maximum of 10 faults can be stored. The duration is also stored for the first 5 faults.
A differentiation is made between crash-relevant faults and non-crash relevant faults. Faults that are not crash-relevant are indicated by longer illumination of the warning lamp which will come on for approx. 2 minutes after the ignition is switched on. They will not affect the operation of the airbag system.
A crash-relevant fault is indicated by permanent illumination of the warning lamp after the ignition is switched on.
The triggering unit covers the following functions:
- Crash detection and determination of ignition point
- Ignition of the airbag system
- Recording of crash data
- Self-test and permanent monitoring of the airbag system
- Fault storage
- Fault display
- Fault output
- System readiness display
The triggering unit should be replaced only after the airbag has been triggered for the third time of if the fault memory cannot be erased anymore.
When replacing the triggering unit, use the System Tester to load the record for the respective vehicle and to lock the triggering unit.
The warning lamp starts to flash before the unit is locked. After the locking process has been completed successfully, the warning lamp goes off (unless a fault has occurred).
Tools
Tools required for troubleshooting:
1. System Tester 9288 in conjunction with adapter lead 9288/1
2. Special Tool 9516
3. Special Tool 9566
4. Commercially available digital multimeter
Note: The Special Tools are used to check the ignition pill circuits. For safety reasons, never drive the vehicle when the Special Tools are connected instead of the airbag units.