Air Bag Control Module: Description and Operation

The Restraints Control Module (RCM) is mounted on the center tunnel under the instrument panel. The RCM performs the following functions:
^ signals the inflators to deploy the air bags in the event of a deployable crash.
^ activates the safety belt buckle pretensioners to remove slack from the safety belt webbing.
^ monitors the air bag Supplemental Restraint System (SRS) for faults.
^ illuminates the air bag indicator if a fault is detected.
^ flashes the air bag indicator 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 generic electronic module (GEM) to activate a chime if the air bag indicator is not available and another SRS fault exists.
^ contains an internal safing sensor which is not serviced separately.

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 air bag indicator located in the instrument cluster.

When the ignition is cycled (turned off and then on), the air bag indicator will remain lit for six seconds and then go out. If an SRS fault exists, the air bag indicator will then flash the two-digit Lamp Fault Code (LFC) associated with that fault. The air bag indicator will flash the LFC five times, then remain illuminated for the rest of the key cycle. The RCM will also communicate the current and historical Diagnostic Trouble Codes (DTCs) through the Data Link Connector (DLC) using a scan tool. If the air bag indicator does not function, and the system detects a fault condition, the RCM will signal the Generic Electronic Module (GEM) 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 air bag indicator require repair.

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 fact will be displayed.

The RCM includes a backup power supply. This feature provides sufficient backup power to deploy the air bags and the safety belt pretensioners in the event that the ignition circuit is damaged in a collision before the safing and air bag sensors determine that an air bag deployment is required. The backup power supply will deplete its stored energy approximately one minute after the battery ground cable is disconnected.