LS V8-3.9L VIN A (2003)
Air Bag Control Module: Description and Operation
RESTRAINTS CONTROL MODULE (RCM)
WARNING: The restraints control module (RCM) orientation is critical for correct air bag supplemental restraint system (SRS) operation. If
a vehicle equipped with an SRS system has been involved in a collision in which the center tunnel area has been damaged, inspect the mounting
and bracket for deformation. If damaged, the RCM must be replaced whether or not the air bags have deployed. In addition, make sure the
area of the RCM mounting is restored to its original condition.
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 restraints control module (RCM) is mounted on the center tunnel under the instrument panel. The RCM carries out the following functions:
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supplies current flow to the inflators to deploy the air bags in the event of a deployable crash.
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activates the safety belt retractor pretensioners to remove slack from the safety belt.
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monitors the air bag supplemental restraint system (SRS) for faults.
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illuminates the air bag indicator if a fault is detected.
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flashes the air bag indicator to indicate the lamp fault code (LFC) detected.
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communicates through the data link connector (DLC) the current or historical diagnostic trouble codes (DTCs).
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signals the instrument cluster module to activate a chime if the air bag indicator is not available and another SRS fault exists.
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contains an internal safing sensor which is not serviced separately.
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records deployment event 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 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 LFC. The air bag indicator will flash the LFC three times, then it will remain illuminated for the rest of the key
cycle. The RCM will also communicate the current and historical DTCs through the (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 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 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 fault will be displayed.
The RCM includes a backup power supply. This feature provides sufficient current to deploy the front air bags and safety belt pretensioners in the event
that the ignition circuit is damaged or lost in a collision before the RCM determines that air bag deployment is required. The backup power supply will
deplete its stored energy approximately one minute after the battery ground cable is disconnected.
