Diagnosis Troubleshooting

The airbag system is continuously monitored by a diagnosis unit in the control unit. If a fault occurs, it is indicated by a warning lamp in the instrument cluster.

- control unit

- both front sensors

- contact unit

In the event of a fault, the central warning lamp and this warning lamp come on. In cars for the USA, the fasten seat belts symbol also lights up.

- both airbag units

If non-activated airbag units have to be removed, they must be ignited electrically before being disposed of (see Page 68-15).

The airbag warning lamp comes on for ap-

prox. 5 seconds when the ignition is switched on, and then goes out. When the engine is started, the warning lamp again comes on for approx. 5 seconds.

Should the warning lamp come on again later, this indicates a fault in the airbag system. The fault can be read out with System Tester 9288 and flashing code tester 9268.

The control unit needs approx. 70 seconds to identify all faults in the system, and the ignition must therefore be switched on for at least this time.

After a fault in the airbag system has been identified and rectified, the fault memory must be erased.

If any components are exchanged, this must be noted in the warranty and maintenance booklet. The document number should be attached in the free space provided. The document number is shown on an adhesive label which can be torn off the spare part.

Following an accident in which the airbag system was activated, the following components must be removed and renewed:

Note:

Reading out the fault memory

System Tester 9288: see Repair Manual Group 03, Self-diagnosis Tester 9268: see Technical Service Information, Model '90.

Meaning of fault codes

1st figure: 3 = Airbag system

2nd figure: 1 = Fault still present

2 = Fault no longer present

3 = Failure time since first fault occurrence

3rd figure:

= Fault code

4th figure:

Before troubleshooting can be carried out correctly, the person concerned must be familiar with the component positions and the function and technical relationship of the systems to be checked (model information)

be able to read and evaluate Porsche circuit diagrams understand the function of the electrical circuits and relays be capable of operating and assessing the information supplied by the test gear.

Important:

If the tester display or the fault list indicates that a component is defective, the fault may not necessarily be found in the component indicated but may be in the associated control unit or the connecting circuits (electrical paths) between the component and the control unit. Before the fault memory has been read out, no troubleshooting involving the pulling off of plugs or similar is to be carried out, as this could also be stored as a fault in the memory.

Note

The fault code can show two types of fault:

- Fault still present

- Fault no longer present

Faults are stored as no longer present if they occur briefly while the ignition is switched on, but are no longer present when the ignition is switched off.

Faults still present are those which are permanent or remain present when the ignition is switched off.

Do not assume that the fault in the readout is actually present or clearly identifiable during the check.

The cause of a fault being memorized may for example be undesirable interference with the airbag system wiring while the ignition was switched on.

It is therefore important in the case of faults no longer present to determine the cause of the fault in order to prevent it from recurring and to avoid renewing parts unnecessarily. Check the entire length of the airbag system wiring for damage (wires no longer intact or trapped).

Tools

560-60 561-68

Special tools 9516 and 9516/1 are used to check the ignition pill circuits.

It there is a fault in the ignition pill circuits, attach special tool 9516 in place of the airbag units, then erase the fault memory. Switch the ignition off and on again.

The fault can then be localized by means of the diagnosis unit in the control unit.

If the warning light no longer indicates a fault, the airbag unit is defective and must be renewed.

If the warning light again indicates a fault, this is to be sought in the control unit or the wiring.

A fault in ignition pill circuit 1 may also be caused by the contact unit. Disconnect the wiring from the contact unit and attach special tool 9516/1 in place of the contact unit. Erase the fault memory. Switch the ignition off and then on again. If the warning light no longer indicates a fault, the contact unit is defective; if the warning light again indicates a fault, this must be in the control unit or the wiring.

Fault code table

Fault code

Designation of fault

Do It Yourself Car Diagnosis

Do It Yourself Car Diagnosis

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