Airbag DM Fault Code 34

Airbag DM Fault Code 34

Drivers airbag circuit low resistance or short circuit.

Normal Operation

The diagnostic module measures the resistance across pins 2-5 and 2-4 every time the ignition is switched on. The resistance should be 1.6 to 1.8Ω. This value is made up of the airbag 1.0Ω and the cable reel cassette windings 0.3-0.4Ω per winding. If the total resistance in the passengers airbag circuit falls below 0.7Ω, fault code 34 will be declared and the airbag lamp will be illuminated.

Note: The nominal resistance of the airbag simulator is 2.5Ω, therefore expect a total circuit resistance reading of 3.1 - 3.3Ω with the simulator fitted.

Caution: The drivers airbag connector contains shorting bars which short circuit pins 1 and 3 of both sides of the connector when disconnected.

DO NOT REMOVE THE AIRBAG CONNECTOR SHORTING BAR UNDER ANY CIRCUMSTANCES.

The airbag harness shorting bar may be temporarily disabled during the following resistance checks.

Possible Causes

• Poorly mated cable reel cassette connector. If the connector is poorly mated, the shorting bars may not be fully retracted.
• Faulty shorting bar may short circuit 2-4 and 2-5 together.
• Short circuit in the cable reel cassette windings.
• A short across the airbag terminals in the airbag module.

Fault Analysis

1. Disarm the airbag system and fit airbag simulators (6.4.21.4).
2. Disconnect the diagnostic module and remove the plastic wedge from connector 2 (black). Measure the resistance between pins 2-5 and 2-4. The resistance should be 3.1 - 3.3Ω.

If the resistance is 3.1 to 3.3Ω, go to step 4.

If the resistance is below 3.1 - 3.3Ω, go to step 3.

3. Disconnect the cable reel cassette connector at the steering column and remove the plastic wedge. Measure the resistance from pins 2-4 and 2-5 at the diagnostic module connector.

If the resistance is infinity, check the cable reel cassette for short circuits. Replace the column switchgear assembly if necessary. Refit the plastic wedges. Reconnect the diagnostic module. Clear the code 34. Rearm the airbags (6.4.21.4).

If the resistance is less than infinity, replace the main airbag harness. Refit the plastic wedges. Reconnect the diagnostic module. Clear the code 34. Rearm the airbags (6.4.21.4).

4. Since the circuit resistance is in specification, the fault must lie in the diagnostic module or in the airbag module.

Substitute a known good diagnostic module. If code 34 recurs with the airbag simulator fitted, there is still a fault in the wiring or the simulator.

If the fault code 34 does not recur, rearm the airbags (6.4.21.4) and retest.

If fault code 34 recurs with the airbag module fitted, the airbag module is faulty. Replace the drivers airbag module (4.5.01.3).