Test Notes

Normal Operation

NOTE: The air bag diagnostic monitor contains an internal thermal fuse that is not serviceable. The thermal fuse is controlled by the microprocessor inside the air bag diagnostic monitor. The microprocessor inside the air bag diagnostic monitor will blow the thermal fuse whenever a short on the deployment circuits occurs. The thermal fuse does not blow because of excessive current flowing through it. DO NOT attempt to short circuit the thermal fuse with a circuit breaker or any other type of fuse.

WARNING: Do not install a new diagnostic monitor until the short has been located and corrected. If a short to ground has not been located and corrected, then the short to ground is intermittent and is not present at this time. Installing a new diagnostic monitor with an intermittent short in the system will result in repeat blown diagnostic monitors and repeat service.

The air bag diagnostic monitor measures the voltages at the air bag diagnostic monitor connector pins. When certain air bag deployment wires are shorted to ground (heavy lines illustrated in the schematic), the system may become susceptible to unwanted deployment of the air bag(s). The air bag diagnostic monitor senses a short to ground on any of these circuits and helps prevent unwanted air bag deployment by blowing the air bag diagnostic monitor thermal fuse. Blowing this fuse removes all power (battery and back-up power) from the air bag deployment circuits. While the short to ground exists, the air bag diagnostic monitor will flash diagnostic trouble code 13 or code 14, depending on where the short appears (refer to Diagnostic Trouble Codes 13 and 14 for more details). If the short to ground is intermittent and temporarily corrects itself, the air bag diagnostic monitor will flash code 51.

NOTE: If the short to ground returns, the higher priority codes 13 or 14 will be flashed instead of 51.

If the air bag indicator is flashing code 51 and a short to ground has not been serviced, this means that an intermittent short to ground exists in the air bag system. The air bag diagnostic monitor should be replaced only after service of the intermittent short has been completed.

Some service tips for finding an intermittent short to ground are:

1. Consult OASIS (Restraint Systems Service Code 104000) for up-to-date diagnostics and descriptions of wiring concern locations for the vehicle (VIN number) on which you are working. OASIS is updated daily using concern descriptions from engineering and Dealership Service sources.

2. Inspect wiring and harnesses in areas through which they pass or are located next to metal components (i.e. engine compartment bulkhead, body sheet metal, component mounting brackets, etc.).