Grand Cherokee 4WD V8-4.7L (2003)
Body Control Module: Description and Operation
Functional Operation
Airbag System
AIRBAG SYSTEM/OCCUPANT RESTRAINT CONTROLLER SYSTEM
The WJ/WG Airbag System contain the following components: Occupant Restraint Controller (ORC), Airbag Warning Indicator, Clockspring, Driver
and Passenger Airbags, Driver and Passenger Hall-effect Seat Belt buckle Switches (SBS), Driver and Passenger Front and Side Impact Sensors,
curtain Airbags, and front impact sensors.
The Occupant Restraint Controller (ORC) is a new type of Airbag Control Module (ACM). The new ACM supports staged airbag deployment and
remote impact sensing. Staged deployment is the ability to trigger airbag system squib inflators individually as needed to provide the appropriate
restraint for the severity of the impact. The ACM has four major functions: PCI Bus communications, onboard diagnostics, impact sensing, and
component deployment. The ACM also contains an energy-storage capacitor. This capacitor stores enough electrical energy to deploy the front airbag
components for two seconds following a battery disconnect or failure during an impact. The ACM is secured to the floor panel transmission tunnel
under the console. The ACM cannot be repaired or adjusted.
The ACM sends and/or receives PCI Bus messages with the Instrument Cluster (MIC), Body Control Module (BCM), and Impact Sensors Diagnostic
trouble codes will be set if the communication with these modules is lost or contains invalid information.
The microprocessor in the ACM monitors the impact sensors signals and the airbag system electrical circuits to determine the system readiness. If the
ACM detects a monitored system fault it sends a message to the instrument cluster via PCI bus to turn on the airbag warning indicator. The ACM can
set both active and stored diagnostic trouble codes to aid in the diagnosing system problems. See DIAGNOSTIC TROUBLE CODES.
The ACM uses two front impact sensors and ACM Accelerometer to sense the rate of vehicle deceleration, provide verification of the direction and
severity of an impact. A pre-programmed decision algorithm in the ACM microprocessor determines when the deceleration rate is severe enough to
require airbag system protection. The ACM also uses the driver and front passenger seat belt switch status (buckled or unbuckled) and crash severity
to determine the level of driver and front passenger airbag deployment, low medium or high. When the programmed conditions are met, the ACM
sends an electrical signal to deploy the appropriate airbag system components.
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. 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 IS 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 MUST BE SCRAPPED AND REPLACED WITH A NEW UNIT.
The airbag warning indicator is the only point at which the customer can observe symptoms of a system malfunction. Whenever the ignition key is
turned to the run or start position, the ACM performs a lamp check by turning the airbag warning indicator on for 6-8 seconds. After the lamp check,
if the indicator turns off, it means that the ACM has checked the system and found it to be free of discernible malfunctions. If the lamp remains on,
there could be an active fault in the system or the MIC lamp circuit may be internally shorted. If the lamp comes on and stays on for a period longer
than 6-8 seconds then goes off, there is usually an intermittent problem in the system.
DRIVER AIRBAG
The airbag protective trim cover is the most visible part of the driver side airbag system. The protective trim cover is fitted to the front of the airbag
module and forms a decorative cover in the center of the steering wheel. The module is mounted directly to the steering wheel. Located under the trim
cover are the horn switch, the airbag cushion, and the airbag cushion supporting components. The airbag module includes a housing to which the
cushion and hybrid inflator are attached and sealed. The 2003 WJ/WG is equipped with driver airbag with dual stage inflators. When supplied with the
proper electrical signal, the inflator or inflators discharge the gas directly into the cushion. The airbag module cannot be repaired, and must be
replaced if deployed or in any way damaged.
WARNING: THE DRIVER AIRBAG MODULE CONTAINS ARGON GAS PRESSURIZED TO OVER 17236.89 kPa (2500 PSI). DO NOT
ATTEMPT TO DISMANTLE AN AIRBAG MODULE OR TAMPER WITH ITS INFLATOR. DO NOT PUNCTURE, INCINERATE, OR
BRING INTO CONTACT WITH ELECTRICITY DO NOT STORE AT TEMPERATURE EXCEEDING 93 degrees C (200 degrees F).
REPLACE AIRBAG SYSTEM COMPONENTS ONLY BUT INTERNAL DIFFERENCES MAY RESULT IN INFERIOR OCCUPANT
PROTECTION. THE FASTENERS, SCREWS, AND BOLTS ORIGINALLY USED FOR THE AIRBAG SYSTEM COMPONENTS HAVE
SPECIAL COATINGS AND ARE SPECIFICALLY DESIGNED FOR THE AIRBAG SYSTEM. THEY MUST NEVER BE REPLACED
WITH ANY SUBSTITUTES. ANY TIME A NEW FASTENER IS NEEDED, REPLACE IT WITH THE CORRECT FASTENERS
PROVIDED IN THE SERVICE PACKAGE OR SPECIFIED IN THE MOPAR PARTS CATALOG.
CAUTION: Deployed Front Air Bags may or may not have live pyrotechnic material within the air bag inflator. Do not dispose of 2003 Model Year
Driver and Passenger Airbags unless you are sure of complete deployment. Please refer to the Hazardous Substance Control System for Proper
Disposal. Dispose of deployed air bags in a manner consistent with state, provincial, local, and federal regulations. Use the following table to identify
