Air Bag Control Module: Description and Operation

RESTRAINTS CONTROL MODULE (RCM)

WARNING: The RCM orientation is critical for correct system operation. If a vehicle equipped with an air bag supplemental restraint system (SRS) has been involved in a collision in which the center tunnel area has been damaged, inspect the mounting and bracket for deformation. If damaged, a new RCM must be installed whether or not the air bags have deployed. In addition, make sure the area of the RCM mounting is restored to its original condition.

CAUTION: Prior to removal of the module, it is necessary to upload module configuration information to the diagnostic tool. This information needs to be downloaded into the new module once installed.

NOTE:
- When installing a new restraints control module (RCM), always make sure the correct RCM is being installed. If an incorrect RCM is installed, erroneous DTCs will result.
- The air bag supplemental restraint system (SRS) utilizes DC firing for air bag and pretensioner deployment.

The restraints control module:
- deploys the air bag(s) in the event of a deployable crash.
- activates the safety belt retractor pretensioners to remove slack from the safety belt.
- monitors the SRS for faults.
- communicates to the instrument cluster module, over the HS-CAN bus, to illuminate the air bag indicator if a fault is detected.
- communicates over the HS-CAN bus through the data link connector (DLC) the current or historical diagnostic trouble codes (DTCs).

The RCM monitors the SRS for possible faults. If a fault is detected while the ignition switch is in the ON position, the RCM will communicate over the HS-CAN bus to the instrument cluster to 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 prove out by lighting for 6 seconds and then off for 2 seconds. After the prove out, the air bag indicator will then remain lit if a SRS fault exists and will remain illuminated for the rest of the key cycle. The RCM will also communicate, over the HS-CAN bus, the current and historical DTCs through the DLC to the diagnostic tool. If the air bag indicator does not function and the system detects a fault condition, the RCM will signal the instrument cluster module to activate an audible chime, located in the GEM. The chime is a series of 5 sets of 5 tone bursts. If the chime is heard, the SRS and the air bag indicator require repair.

The RCM includes a backup power supply. This feature provides 150 ms of backup power to deploy the front air bags and pretensioners in the event that the ignition circuit is lost or damaged during impact.

The backup power supply will deplete its stored energy approximately one minute after the battery ground cable is disconnected.