Porsche 968 Air Bag Fault 10 Ignition Circuits

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 to ensure that all poosible sources of defects can be checked.

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

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

- control unit

- both front impact sensors

- contact unit

- both airbag units

If non-activated airbag units have to be removed, they must be ignited electrically before being disposed of (see page 68 - 61).

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.

* 2,5 seconds as of manufacturing date June 22, 1992.

Before troubleshooting can be carried out correctly, the person concerned must be

• familiar with the component locations 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 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 shows two types of fault:

- Fault still present

- Fault currently not present

Faults are stored as currently not 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.

A fault being memorized may for example be due to tampering with the airbag system wiring while the ignition was switched on.

In the case of faults currently not present, it is also important to determine the cause of the fault in order to prevent it from recurring and to avoid replacing parts unnecessarily. Check the entire length of the airbag system wiring for damage (wires damaged or trapped).

Tools

Tools

580-68 561-68

Special Tool 9516 Special Tool 9516/1

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

If 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 identified by means of the diagnosis unit in the airbag control unit.

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

If the warning light again indicates a fault, the control unit or the wiring are at fault.

A fault in ignition pill circuit 1 may also be caused by the contact unit. Disconnect the wiring harness 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, the control unit or the wiring are at fault.

Note

For safety reasons, never drive the vehicle with the special tools installed in place of the airbag units.

Special Tool 9541 1074-68

Special Tool 9541 is used to check the wiring of the airbag system. It is attached in place of the control unit. For safety reasons, the wiring to the ignition pills cannot be checked with this tool.

1. Fault memory Fault code table

Fault code

Designation of fault

10

Ignition circuits

- closed once

- closed several times

- permanently closed

- contact resistance to Ub

- contact resistance to ground

- coupled 1/3 or 2/3

11

Left front sensor

- resistance too high

12

Right front sensor

- resistance too high

21

Ignition pill circuit 1

- resistance too high / too low

22

Ignition pill circuit 2

- resistance too high / too low

23

Ignition pill circuit 3

- resistance too high / too low

30

Warning light airbag

- Signal implausible

31

- Control unit defective

40 to 47

- Control unit defective

50 to 54

- Control unit defective

60 to 62

- Control unit defective

70

Crash entry

- only if airbag has been triggered

Fault, Fault Code

Possible Causes, Elimination, Remarks

After an airbag system fault has been detected and rectified, the fault memory must be erased.

Test point 1

Ignition circuits closed once Fault code 10

- Replace both front impact sensors.

- Check wiring harness for squeezed sections or chafing and replace if required.

Test point 2 Ignition circuits closed several times Fault code 10

- Refer to test point 1.

Test point 3 Ignition circuits closed permanently Fault code 10

- Refer to test point 1.

Test point 4 Ignition circuits

Contact resistance to Ub

Fault code 10

- Check wiring harness to front impact sensors and ignition pills for squeezed sections and chafing. Replace if required.

- Using Special Tool 9541, check wiring to front impact sensors for short to positive terminal, replace if required.

- Check front impact sensors for short to positive terminal.

- If no fault can be detected at the front impact sensors and at the wiring, the control unit must be replaced.

Test point 5 Ignition circuits

Contact resistance to ground Fault code 10

- Check wiring harness to front impact sensors and ignition pills for squeezed sections and chafing. Replace if required.

- Using Special Tool 9541, check wiring harness to front impact sensors for short to ground.

- Check front impact sensors for short to ground.

- If no fault can be detected at the front impact sensors and at the wiring harness, replace the control unit.

Fault, Fault Code Possible Causes, Elimination, Remarks

Test point 6

Ignition circuits - Check wiring harness and ignition pills for

Coupled 1/3 or 2/3 squeezed sections and chafing. Replace if required.

Fault code 10 - if no fault can be detected, replace control unit.

Test point 7 Left front sensor

Resistance too high Fault code 11

2. Ohmmeter to terminals 2 and 3 Display: 0...0.5 Q

- Check control unit wiring to front impact sensor connector with Special Tool 9541 and ohmmeter

- If no fault is detected at the front impact sensor and at the wiring, replace control unit.

- Using an ohmmeter, check front impact sensor at connector.

1. Ohmmeter to terminals 1 and 2 Display: 10 kQ

Test point 8 Right front sensor

Resistance too high Fault code 12

- refer to test point 7.

Fault, Fault Code

Possible Causes, Elimination, Remarks

Test point 9 Ignition pill circuit 1

Resistance too high / too low Fault code 21

1. Remove driver airbag - unit.

2. Attach Special Tool 9516 in place of airbag unit.

Interface Obd Connecteur Porsche 944

3. Erase fault memory.

4. Check if fault is still present.

a) Replace airbag unit if the fault is no longer present.

b) If the fault is still present, disconnect the contact unit wiring and attach Special Tool 9516/1.

5. Erase fault memory.

6. Check if fault is still present.

a) Replace contact unit if the fault is no longer displayed.

b) If the fault is still present, check wiring harness for squeezed sections and chafing. Replace if required.

Fault, Fault Code

Possible Causes, Elimination, Remarks c) If no fault is detected in the wiring harness, replace the control unit.

Test point 10 Ignition pill circuit 2

Resistance too high/too low Fault code 22

Note

Ignition pill circuit 2 at the passenger side airbag is the leftmost of the two circuits.

1. Disconnect plug at passenger side airbag unit.

2. Attach Special Tool 9516.

3. Erase the fault memory.

4. Check if fault is still present.

a) If the faut is no longer present, replace passenger side airbag unit.

b) If the fault is still present, check wiring harness for squeezed sections and chafing. Replace if required.

c) If no fault is detected in the wiring harness, replace the control unit.

Test point 11

Ignition pill circuit 3 Resistance too high/too low Fault code 23

Ignition pill circuit 3 at the passenger-side airbag is the rightmost of the two circuits.

- refer to test point 10.

Test point 12

Airbag warning light Signal implausible Fault code 30

Check warning lamp, replace if required.

Check wire from control unit to instrument cluster or to diagnosis socket, respectively, for short to positive terminal.

■ Check instrument cluster.

Test point 13 Control unit defective

- Replace control unit. Note

This fault message may display several fault codes: 31, 40 to 47, 50 to 54 and 60 to 62.

Fault, Fault Code Possible Causes, Elimination, Remarks

Test point 14:

Unknown fault code - Check secondary ignition circuit, fault code xxx

- Erase fault memory.

Fault, Fault Code Possible Causes, Elimination, Remarks

2. Failure time

The Failure Time menu item displays the time elapsed since the first fault was stored In the fault memory.

The maximum time that can be displayed is 99 hours and 59 minutes. If this time is exceeded, the " >" sign is displayed ahead of the hours.

3. Results

The Results menu item displays the crash data.

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Responses

  • gioacchino
    Why would the air bag light be on after replacing the cluster on a 968 porsche?
    2 years ago

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