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.
- DTCs may not be displayed for approximately 45 seconds after the ignition switch is placed in the RUN position. This is the amount of time the air bag diagnostic monitor requires to perform all tests and verify system faults, if present.
- 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.

CAUTION: The thermal fuse does not blow (open) because of excessive current flowing through it. Do not attempt to jumper out the thermal fuse with a circuit breaker or any other type of fuse.

- 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.
- 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.
- 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 fender primary crash front air bag sensor and brackets or the radiator primary crash center air bag sensor and bracket and the center cowl 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.






- The air bag indicator will illuminate continuously for approximately six seconds whenever the ignition switch is turned to the ON position if the air bag system is working properly. If an air bag system fault is present, the air bag indicator will either fail to illuminate, remain lit continuously, or flash.
- The tone generator is internal to the diagnostic monitor. The air bag warning indicator is the prime indicator for determining the air bag system condition. However, a series of five sets of five beeps will be heard if the air bag indicator is inoperative and a fault occurs in the system. This indicates that the air bag system requires service.

NOTE: Unless serviced, the air bag system may not function properly in the event of a collision.