Continuous Airbag Warning Lamp

Continuous Airbag Warning Lamp

Inoperative lamp circuit or no ignition supply to the airbag diagnostic module.

Normal Operation

The airbag warning lamp is designed to illuminate for approximately six seconds when the ignition is switched on. This period is allocated for satisfactory performance of the airbag system self test. If after this period, the diagnostic module detects a fault within the system, the airbag warning lamp will begin to flash.

Note: The seat belt pretensioner system (if fitted) shares the airbag/SRS warning lamp with the airbag system. If a seat belt pretensioner fault is detected, the Airbag/SRS warning lamp will be permanently illuminated. Ensure that a permanently lit lamp is not the result of a pretensioner fault before carrying out fault analysis on the airbag system.

Poor connection or disconnection of the diagnostic module harness may cause a short circuit from DM pin 4 (warning lamp control) to pin 5 (ground) and cause permanent illumination of the warning lamp.

Faulty operation of the diagnostic module internal logic may fail to turn off the warning lamp control circuit and cause constant illumination of the warning lamp.

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). Reconnect the battery.
2. Inspect the instrument pack and diagnostic module connectors for damaged, pushed out pins, proper location etc.

If any defects are identified, service as necessary. Retest to ensure correct operation of the airbag warning light.

If the connector condition and security are good, reconnect the connectors and go to step 3.

3. Connect the PDU to the upper diagnostic socket and monitor the airbag warning lamp signal. Switch on the ignition.

If the signal is permanently low, suspect a short circuit to ground on the airbag warning lamp control line within the diagnostic module or from diagnostic module pin 1-4 to earth. Go to step 4.

If the signal switches low for six seconds after ignition on but the airbag warning lamp is permanently illuminated, suspect a fault in the output side of the instrument pack to the airbag warning lamp.

4. Disconnect diagnostic module plug 1 (slate) and withdraw the plastic locking wedge to prevent shorts to other circuits. Check continuity from pin 1-1 to ground.

If a short circuit to ground is detected, service the wiring as necessary. Replace the locking wedge, reinsert the connector. Switch on the ignition and check that the airbag warning lamp signal at pin 1-4 goes high six seconds after switching on the ignition and that the warning lamp extinguishes.

If no short circuit to ground is detected, the diagnostic module is faulty. Replace the diagnostic module. Switch on the ignition and check that the airbag warning lamp signal at pin 1-4 goes high six seconds after switching on the ignition and that the warning lamp extinguishes.

5. Switch off the ignition. Disconnect the battery. Rearm the airbags (6.4.21.4). Switch on the ignition and check for correct indications from the airbag warning lamp.