Airbag Control Module (ACM)

AIRBAG CONTROL MODULE
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 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, behind the instrument panel center bezel, underneath the radio. 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 microprocessor 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.


The Airbag Control Module (ACM) is secured to a bracket on the floor panel transmission tunnel below the instrument panel inside the vehicle. The ACM mounting bracket also serves as the instrument panel center support. The ACM's microprocessor determines when the deceleration rate signaled by the impact sensor indicates that the impact is severe enough to require airbag protection. When the programmed conditions are met, the ACM sends an electrical signal to deploy the airbag system components.

Only one impact sensor is used in this airbag system. The impact sensor is an accelerometer that senses the rate of vehicle deceleration, which provides verification of the direction and severity of the impact. The impact sensor is calibrated for the specific vehicle, and is only serviced as a unit with the ACM.

The ACM also contains an energy storage capacitor. This capacitor stores enough electrical energy to deploy the airbags, for one second following a battery disconnect or failure during an impact. The purpose of the capacitor is to provide the airbag system protection in a severe secondary impact if the initial impact has damaged or disconnected the battery, but was not severe enough to deploy the airbags.

WARNING THE AIRBAG SYSTEM IS A SENSITIVE, COMPLEX ELECTROMECHANICAL UNIT. BEFORE ATTEMPTING TO DIAGNOSE OR SERVICE ANY AIRBAG SYSTEM OR RELATED STEERING WHEEL, STEERING COLUMN, OR INSTRUMENT PANEL COMPONENTS YOU MUST FIRST DISCONNECT AND ISOLATE THE BATTERY NEGATIVE (GROUND) CABLE. THEN WAIT TWO MINUTES FOR THE SYSTEM CAPACITOR TO DISCHARGE BEFORE FURTHER SYSTEM SERVICE. THIS IS THE ONLY SURE WAY TO DISABLE THE AIRBAG SYSTEM. FAILURE TO DO THIS COULD RESULT IN ACCIDENTAL AIRBAG DEPLOYMENT AND POSSIBLE PERSONAL INJURY.


Never strike or kick the airbag control module, as it can damage the impact sensor or affect its calibration. If an airbag control module is accidentally dropped during service, the module has to be scrapped and replaced with a new unit.