Air Bag Control Module: Description and Operation

This vehicle has a single point sensing system. The diagnostic monitor, crash sensors and safing sensor are incorporated into an electronic air bag control module mounted centrally in the vehicle. The air bag control module retains full control of the complete air bag system.

The electronic air bag control module is mounted horizontally to the floor pan beneath the floor console, to facilitate impact sensing along the longitudinal axis. The air bag control module retains full control of the air bag system at all times, providing continual systems checks and maintaining a full diagnostic function. The air bag control module stores any faults detected during a driving cycle in a non volatile memory, which can be accessed through the Data Link Connector (DLC) using appropriate test equipment. The air bag control module indicates the presence of a fault by flashing the air bag warning indicator after the initial prove out sequence. The behavior of the warning indicator depends on the type of fault present.

Air Bag Indicator:

If the air bag warning indicator fails, the air bag control module uses the secondary air bag warning indicator. The secondary air bag warning indicator will only flash if there is a fault present and the primary air bag warning indicator is inoperative.

The air bag control module provides a back up power supply, sufficient to deploy the air bag(s) for a maximum of 150 mS after power loss. The back up power supply is discharged by the electronic air control module within 60 seconds of the battery ground cable being disconnected.

The air bag control module contains a micro controller to evaluate and process impact data an electronic accelerometer, which measures the actual acceleration and deceleration along the vehicle's longitudinal axis and an electro-mechanical safing sensor. When both these sensors detect an impact in excess of a predetermined limit, the deployment sequence will be initiated by the air bag control module to deploy the frontal air bag(s). The two sensors working together prevent unintentional deployment of the frontal air bag(s).

The air bag warning indicator is located in the instrument cluster. It illuminates for approximately six seconds when the ignition is turned ON and then will go OFF unless a fault is detected. If a fault is detected the warning indicator will start to flash after another 5 seconds.