Air Bag Control Module: Description and Operation

DESCRIPTION
The Airbag Control Module (ACM) contains the impact sensor and energy reserve capacitor. The ACM monitors the system to determine the system readiness. The ACM contains on-board diagnostics and will light the AIRBAG warning lamp in the message center when a problem occurs. The driver and passenger airbag system is a safety device designed to reduce the risk of fatality or serious injury. caused by a frontal impact of the vehicle.

OPERATION
The impact sensor provides verification of the direction and severity of the impact. One impact sensor is used. It is located inside the Airbag Control Module (ACM) which is mounted on a bracket, just forward of. the center console. The impact sensor is an accelerometer that senses deceleration. The deceleration pulses are sent to a microprocessor which contains a decision algorithm. When an impact is severe enough to require airbag protection, the ACM micro processor sends a signal that completes the electrical circuit to the driver and passenger airbags. The sensor is calibrated for the specific vehicle and reacts to the severity and direction of the impact.

CIRCUIT OPERATION
Two different circuits supply battery voltage to the Airbag Control Module (ACM), they are F14 and F23. Different circuits from the Power Distribution Center (PDC) and the ignition switch supply battery voltage to the junction block bus bars.

The F23 circuit supplies battery voltage to the ACM only when the ignition switch is in the RUN position. The F14 circuit powers the ACM when the ignition switch is in either the START or RUN position.

A bus bar internal to the ignition switch connects the A2 circuit from the junction block to the A22 circuit when the switch is in the RUN position. The A22 circuit supplies battery voltage to the PDC fuse that feeds the F23 circuit. A 10 amp fuse in the junction block, cavity 27, protects the A2 and A22 circuits. A 10 amp fuse in cavity 28 of the PDC protects the F23 circuit.

When the ignition switch is in the START/RUN position, it connects the A1 circuit from the PDC to the F87 circuit. The F87 circuit supplies battery voltage to the junction block bus bar that feeds the F14 circuit. A 40 amp fuse in cavity 5 of the PDC protects the A1 and F87 circuits. A 10 amp fuse in cavity 27 of the PDC protects the F23 circuit.

The ACM has a case ground, and an external dedicated ground, circuit Z2. The dedicated ground connects to the ACM bracket.