CAB: Continuous Air Bag Indicator

Electrical Schematic:

Normal Operation
The air bag lamp is designed to illuminate for 6 (± 2) seconds when the ignition key is turned to the ON position. This initial 6 seconds of air bag lamp illumination (continuous lamp) is considered normal operation and is called "prove out" of the air bag lamp. If the diagnostic monitor detects any faults in the air bag system following prove out, it will flash the air bag lamp a series of times to indicate the fault code that has been detected. If the air bag lamp comes on when the ignition key is turned to the ON position and stays on for more than 8 seconds continuously, then a fault exists in the air bag lamp circuit.

The air bag diagnostic monitor incorporates a solid state circuit that shorts the air bag lamp line (circuit 952 "R/GN") to ground to turn the air bag lamp on. When the gray diagnostic monitor harness connector is unplugged from the diagnostic monitor, a shorting bar within the harness connector connects pins 4 (air bag lamp) and 5 (ground) together. Therefore, the shorting bar will turn the air bag lamp on whenever the gray diagnostic monitor harness connector is disconnected. Because the shorting bar makes a continuous connection between pins 4 and 5 when the connector is disconnected, the air bag lamp will not flash. Instead the lamp will be illuminated continuously.

If the computer within the diagnostic monitor fails to "boot up" with the key ON, the lamp driver circuit will automatically turn the air bag lamp ON continuously indicating a problem in the air bag diagnostic monitor or at the gray diagnostic monitor connector.

Possible Causes
Continuous illumination of the air bag lamp can be cause by the following:
1. A disconnected or poorly connected diagnostic monitor may not push the shorting bar between pins 4 and 5 into its fully retracted position. This shorts the air bag lamp line to ground and causes the air bag lamp to illuminate continuously.
2. Shorted air bag lamp wiring.
3. A faulty diagnostic monitor.

Pinpoint Test Steps:

CAB1: