Airbag DM Fault Code 12

Airbag DM Fault Code 12

Low battery voltage

Normal Operation

The airbag diagnostic module (DM) monitors the voltage at pin 1-7 which should be equal to the battery voltage. If a voltage lower than 9 volts is detected at pin 1-7, the airbag warning lamp will be illuminated and fault code 12 will be flashed.

Possible Causes

Drop in battery voltage to DM pin 1-7 caused by:

• Open circuit to pin 1-7 from the battery
• Short circuit to ground on the battery feed circuit
• Safing sensor feed shorted to ground
• Safing sensor internal short to ground
• Faulty charge system draining the battery

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. Complete a battery voltage test as follows:
   1. Measure the battery voltage at the battery under KOEO and KOER conditions. If the battery voltage is below 10.5 volts during KOEO or below 12.5 volts during the KOER tests, service the battery and charging system as necessary. Retest for airbag system fault code 12 and go to step 2 if the fault recurs.
2. Complete a 12 volts supply check at the diagnostic module:
   1. Disarm the airbag system and fit airbag simulators (6.4.21.4)
   2. Disconnect the airbag diagnostic module.
   3. Switch on the ignition.
   4. Measure the voltage between DM harness connector pin 1-7 (+) and harness connector pin 1-3 (-).
   5. If battery voltage is not present, go to step 3. If battery voltage is present at pin 1-7, renew the diagnostic module. Rearm and verify the airbag system.
3. Check the supply fuse as follows:
   1. Check fuse F16 in the passenger side fusebox RHD (or F18 in passenger fusebox LHD). If the fuse has not blown, check for an open circuit between battery positive and diagnostic module connector pin 1-7. If the fuse has blown, Renew the fuse and/or repair the wiring and go to step 4.
4. Check for a short circuit as follows:
   1. Switch off the ignition. With the airbag diagnostic module disconnected, measure the continuity to earth from diagnostic module connector pin 1-7 to ground. If no short circuit is detected, go to step 5. If a short to ground is detected, service the wiring as necessary. Reconnect the diagnostic module and retest to ensure that code 12 is cleared.
5. Check for a short circuit to ground on the safing sensor wiring as follows:
   1. Check for a short circuit to ground at diagnostic module pin 1-9.
   2. If a short is detected, disconnect the safing sensor and repeat the check at diagnostic module pin 1-9. If a short is still detected, service the wiring from diagnostic module pin 1-9 to safing sensor pin 7.
   3. If no short circuit is detected, change the airbag diagnostic module. Reconnect the diagnostic module and retest to ensure that code 12 does not recur.
6. Rearm the airbags (6.4.21.4)