Air Bag Control Module: Description and Operation

PURPOSE
Performing system diagnostics is the main purpose of the air bag diagnostic monitor.

The air bag diagnostic monitor continually monitors all air bag system components and wiring connections for possible faults when the ignition switch is in RUN position.

OPERATION
It does not deploy the air bags in the event of a collision. The air bag diagnostic monitor operates in the following manner:
- If the air bag diagnostic monitor detects a fault in the air bag system, a Diagnostic Trouble Code (DTC) will be written to the air bag diagnostic monitor's Non-Volatile Random Access Memory (NVRAM).
- This DTC will then be displayed on the air bag indicator lamp.
- After servicing, the DTC may then be cleared from NVRAM.

AIR BAG SYSTEM FUNCTIONS
Other important features of the air bag diagnostic monitor and its functions within the system are described below. It is necessary that these key features and functions are well understood.

- The air bag diagnostic monitor illuminates the air bag indicator for approximately six seconds when the ignition switch is in the RUN position and then turns the indicator Off. This shows that the air bag indicator is operational. If the air bag indicator does not illuminate or the indicator stays on or flashes at any time, a fault has been detected by the air bag diagnostic monitor.
- Each diagnostic trouble code (a series of flashes and pauses of the air bag indicator) represents a two digit number.
For example, a diagnostic trouble code 32 is displayed as three flashes, followed by a one second pause, then two flashes, followed by a three second pause. This sequence will repeat as long as the ignition switch is in the On position and the fault exists.
- If a system fault is present and the air bag indicator is malfunctioning, an audible tone will be heard, indicating that system service is required.
- If a fault exists that makes unwanted air bag deployment possible, the air bag diagnostic monitor has an internal thermal fuse that will blow (open) automatically. This removes all power to the air bag deployment circuit. The air bag indicator will flash the appropriate fault code to indicate the suspect circuit.
- If a system fault is present and the air bag indicator is malfunctioning, an audible tone will be heard, indicating that system service is required. The tone is a series of five sets of five beeps. This does not indicate a fault code 55. If the tone is heard, the air bag warning indicator is inoperative and a system fault that requires service is present.
- Fault codes are prioritized numerically so that if two or more different faults occur at the same time, the fault having the highest priority will be displayed first. After that fault has been corrected, the next highest priority fault code will be displayed. The fault code will repeat continuously until repaired.
- The air bag diagnostic monitor includes an internal backup power supply. This feature provides sufficient backup power to deploy the air bag in the event that the battery or battery cables are damaged in an accident before the radiator primary crash front air bag sensor and brackets or the safing rear air bag sensor and bracket close. The backup power supply will deplete its stored energy approximately one minute after the battery ground cable is disconnected.

WARNING: The backup power supply energy must be depleted before any air bag component service is performed. To deplete the backup power supply energy, disconnect the battery ground cable and wait one minute.