System Description

WARNING: Whilst it is completely safe to access and read the airbag diagnostic module memory at the diagnostic socket, significant personal risks exist in the performance of any other tasks on the airbag system or components. Therefore all workshop manual warnings must be read and all safety procedures must be followed before, during and on completion of any other practical work on the airbag system.

System Description

The airbag system installation comprises:

• Airbag Diagnostic Module
• Driver and passenger airbag modules
• Two front impact (crash) sensors
• One 'safing' sensor
• Dedicated wiring harness
• SRS indicator/warning lamp

The system is designed to provide protection for both driver and front seat passenger by automatically deploying airbags in the event of a collision during forward travel.

In the event of a collision, the crash and safing sensors will operate, completing the firing circuit and causing the airbags to inflate within 32 milliseconds. At least one crash sensor and the safing sensor must operate to fire the airbags.

Any faults in system components, installation or wiring will be indicated by a flashing code on the SRS/AIRBAG warning lamp. Fault code information may also be monitored using the PDU or scan tool.

A full description of the airbag system components is included in the workshop manual.

Airbag Diagnostics

The Airbag Control Module indicates a fault by transmitting a pulsed signal down the Airbag System Failure line to flash the SRS/AIRBAG warning lamp. The fault code is repeated continuously. If there are two or more faults, the fault code with the highest priority is transmitted first. The second fault code is only transmitted when the first fault has been rectified.

The SRS/AIRBAG warning lamp is also used to indicate any problem in the seat belt pretensioner system (if fitted). Flashing of the lamp indicates an airbag fault, constant illumination of the lamp indicates a seat belt pretensioner fault.

At the top left of the PDU screen there is a bullet mark which indicates the current state of the Airbag System Failure line. As a code is transmitted the bullet mark can be seen to flash. The PDU reads the fault code, and writes the code number and fault description to the screen. The PDU continues to monitor the transmitted code. If the transmitted code changes, the new code number and description will appear below the first.

When remedial action has been taken to correct a fault, press the Clear Button to clear down the PDU display. Then use the PDU to ensure that no faults are reported.

A series of audible beeps, continuously transmitted by the Airbag Diagnostic Module, indicates that there is an Airbag System fault to report and that the Airbag System Failure line is open circuit. The PDU is not able to monitor the fault line in this situation as there is no pull-up resistor, normally provided by a warning lamp in the instrument pack.

Rapid continuous flashing of the Instrument Pack Airbag Failure Lamp indicates that both front impact sensors are disconnected. No fault code is reported on the PDU, however on close inspection the bullet mark can be seen to flicker.