Normal Operation

Airbag circuit short to ground

Normal Operation

The diagnostic module measures the voltage at pins 2-5 and 2-6. The voltage at these pins is dependant on charging system voltage as shown in the table below.

If the diagnostic monitor measures a voltage of 2.0 volts or less on pins 2-5 and 2-6, a fault code 13 will be generated and flashed to the instrument pack to be signalled on the airbag warning lamp. Voltages as low as 2.0 volts indicate a possible short to ground in these circuits.

When generating a code 13 the diagnostic module also generates a signal to blow its own internal thermal fuse. This action disables the airbag deployment circuit. The airbag diagnostic module fuse is non-repairable and the module must be replaced after repairing the short circuit. If the voltage at pins 2-5 and 2-6 returns to normal, fault code 51 (blown thermal fuse) will be stored in memory.

Fault Analysis

WARNING: Read and adhere to all warnings and safety procedures at the start of this section when working on the airbag system.

1. Disarm the airbag system and fit airbag simulators (6.4.21.4)
2. Disconnect the airbag diagnostic module. Switch on the ignition.
3. Measure the continuity to ground at the following pins on the diagnostic module harness connector:
   • 2-2 Passenger airbag feed
   • 2-3 Passenger airbag return
   • 2-4 Drivers airbag return
   • 2-5 Drivers airbag feed
   • 2-11 Safing sensor feed

   If no short circuit is detected, go to step 4.

   If a short circuit is detected, disconnect the relevant airbag simulator or the safing sensor and repeat the continuity measurement to isolate the circuit fault. Service the wiring or replace the safing sensor as necessary. Fit a new airbag diagnostic module and rearm the airbags (6.4.21.4).

4. Check for intermittent short circuits in the cable reel cassette. Monitor the continuity to ground at pins 2-4 and 2-5 whilst rotating the steering from lock to lock in both directions.

If no short circuit is detected, go to step 5.

If a short circuit is detected, replace the column switchgear assembly. Fit a new airbag diagnostic module and rearm the airbags (6.4.21.4).

WARNING: Do not attempt to make any electrical measurements on the airbag modules. Any induced voltage can cause the airbag to deploy with the risk of personal injury.

5. Fit a replacement diagnostic module and replacement airbag modules.

Caution: Do not refit the old airbag modules. They may be faulty and would damage the new diagnostic module.

6. Rearm the airbag system (6.4.21.4).