Airbag System Preparation and Flashcode Readout

Airbag Diagnosis

The intention of this information is to aid the technician in diagnosis and repair of the airbag system. Through this clarification of diagnosis and repair procedures, airbag system repairs can be made easier and more effective.

The fault table for lamp codes (fault flash code) is written out and followed by the fault description and hex code number.

The following text is based on information found in Service Information Airbag WKD 493 621 and the 944 Workshop Manual Supplement X WKD 481 821 10, pages 68-5 to 68-13.

FIGURE 1:

Fig. 1 Locally made tool consists of:
1. - lead approx. 0.5 mtr. long
2. - alligator clip
3. - N.O.C. function microswitch (circuit complete when switch is pressed) E.G. limit switch of lifting roof
4. - plug receptacle PN 171 971 998 B
5. - round pin connector N 017 589 4
6. - flat connector, qty. 2, PN 111 971 959

FIGURE 1:

FIGURE 2:

1. Preparation for Diagnosing Airbag System

A. Switch off ignition.

B. Connect locally made tool (Fig. 1) between airbag control unit test plug pin 2 and chassis ground. (Fig. 2)

C. Depress microswitch to give ground to pin 2 of airbag test plug.

D. Switch on ignition.

E. After 3 seconds from the time the ignition is switched on, release the microswitch. (lift ground)

FIGURE 3:

2. Diagnosing Through Flash code Readout

A. Reading

A fault in the airbag system can be read out via the airbag light. The flash code (Fig. 3) runs off automatically after stimulation of pin 2 of the airbag test plug with a timed ground signal (3 sec). The first fault code readout begins after the first 3 seconds light interval.

B. Interpreting Fault Code Table
* Important Note:

When determining the fault code, always note the fault type. Two types of faults are possible: short or long term.

Short term faults are present for a short time (intermittent) with "ignition on only". Therefore it cannot be assumed that the displayed fault is present at the time of repair or is easily detectable. If a short term fault is displayed, it is especially important to determine and repair the cause of the fault to prevent reoccurrance or unnecessary component replacement.

A cause for short term fault indication could be tampering with the airbag system wiring harness with ignition on. In this case it might not be necessary to replace components and only fault erasing would be necessary.

Long term faults must be repaired before erasing.