Air Bag Control Module: Description and Operation

RESTRAINTS CONTROL MODULE (RCM)

NOTE: Care must be taken when disconnecting and connecting the RCM electrical connectors.

The RCM is mounted on the center tunnel under the instrument panel. The RCM carries out the following functions:
- deploys the air bags in the event of a deployable impact.
- activates the safety belt buckle pretensioners to remove slack from the safety belt webbing.
- monitors the SRS for faults.
- illuminates the restraints indicator lamp (RIL) if a fault is detected.
- illuminates the passenger air bag deactivation (PAD) indicator when conditions warrant illumination.
- flashes the restraints indicator lamp to indicate the lamp fault code (LFC) detected.
- communicates through the data link connector (DLC) the current or historical diagnostic trouble codes (DTCs).
- signals the instrument cluster module to activate a chime if the restraints indicator lamp is not available and another SRS fault exists.
- records deployable and non-deployable impact data.

The RCM monitors the SRS for possible faults. If a fault is detected while the ignition switch is in the RUN position, the RCM will illuminate the restraints indicator lamp located in the instrument cluster.

When the ignition is cycled (turned off and then on), the restraints indicator lamp will remain lit for six seconds and then go out. If an SRS fault exists, the restraints indicator lamp will then flash the two-digit lamp fault code (LFC) associated with that fault. The restraints indicator lamp will flash the LFC five times, then remain illuminated for the rest of the key cycle. The RCM will communicate current and history diagnostic trouble codes (DTCs) through the data link connector (DLC) using a scan tool. If the restraints indicator lamp does not function, and the RCM detects a fault condition, the RCM will signal the instrument cluster module to activate an audible chime. The chime is a series of five sets of five tone bursts. If the chime is heard, the SRS and the restraints indicator lamp require service.

LFCs are prioritized. If two or more 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 will be displayed.

The RCM includes a backup power supply. This feature provides sufficient power to deploy the front air bags and the safety belt buckle pretensioners in the event that the ignition circuit is damaged in a collision before the air bags are deployed. Once ignition voltage is removed the backup power supply will deplete its stored energy reserve in approximately one minute. The battery ground cable must be removed before deactivating a SRS.