Test Notes and Schematics

Electrical Schematic-Continuous Air Bag Indicator


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

The air bag diagnostic monitor incorporates a solid state circuit that shorts the air bag indicator line (Circuit 608, BK/Y) to ground to turn the Air Bag Indicator 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 indicator) and 5 (ground) together. Therefore, the shorting bar will turn the Air Bag Indicator on whenever the Gray diagnostic monitor harness connector is disconnected. Because the shorting bar makes a continuous connections between Pins 4 and 5 when the connector is disconnected, the Air Bag Indicator will not flash-instead, it will be illuminated continuously.

When the ignition switch is turned ON, the diagnostic monitor "wakes up" and after approximately 6 seconds turns the Air Bag Indicator OFF If the diagnostic monitor fails to "wakeup", the lamp driver circuit will automatically turn the Air Bag Indicator ON continuously indicating a concern in the air bag diagnostic monitor or at the Gray diagnostic monitor connector.

Possible Causes
Continuous illumination of the Air Bag Indicator can be caused by:
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 Indicator line to ground and causes the Air Bag Indicator to glow continuously.
2. Shorted Air Bag Indicator wiring.
3. A damaged or worn diagnostic monitor.