Airbag System: Notes

The Airbag System contains the following components: two types of Occupant Restraint Controller or (ORC), base and premium, Airbag Warning Indicator, Clockspring, Driver and Passenger Dual Squib Airbags, Seat belt Tensioners, Left and Right Side and Front Impact Sensors, and Seat Airbags. The (ORC) is a new type of Airbag Control Module (ACM) that supports staged airbag deployment. The term Airbag Control Module or ACM will be used throughout the airbag diagnostic and in the Diagnostic Readout Box or DRBIII®. The Base ACM can be identified by the present of a single yellow 23 - way connector. This module supports the Driver and Passenger Seat Belt Tensioners and dual squib airbags.

The ACM has four major functions: PCI Bus communications, on-board diagnostics, impact sensing, and component deployment. The ACM sends and/or receives PCI Bus messages with the Instrument Cluster (MIC), Body Control Module (BCM), and Powertrain Control Module (PCM). Diagnostic trouble codes will be set if the communication with these modules is lost or contains invalid information. 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 has an internal accelerometer that senses the rate of vehicle deceleration, which provides 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 crash severity to determine the level of driver and front passenger deployment, staged deployment low medium or high. Staged deployment is the ability to trigger airbag system squib inflators all at once or individually as needed to provide the appropriate restraint for the severity of the impact. When the programmed conditions are met, the ACM sends an electrical signal to deploy the appropriate airbag system components. The ACM stores enough electrical energy to deploy the airbag components for two seconds following a battery disconnect or failure during an impact.

The Premium ACM can be identified by the present of a two yellow 32-way connectors and the presents of side seat airbag. In addition to the base system components and DTC's the premium ACM supports the Side and Front Impact Sensors, Side Seat Airbags. In addition to the ACM accelerometer the premium module uses Side Impact Sensors to identify the direction and severity of a side impact and deploy the appropriate side seat airbag. In addition to the base ACM DTCs the premium ACM provides DTC's for the additional circuit and component.

Both modules are secured to the floor panel transmission tunnel under the Instrument Panel. Airbag Control Modules cannot be repaired or adjusted and must be replaced.

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 IN ACCIDENTAL AIRBAG DEPLOYMENT AND POSSIBLE PERSONAL INJURY OR DEATH.

WARNING: NEVER STRIKE OR KICK THE AIRBAG CONTROL MODULE OR SIDE IMPACT SENSORS, AS IT CAN DAMAGE THE INTERNAL ACCELERATION SENSOR OR AFFECT ITS CALIBRATION. IF AN AIRBAG CONTROL MODULE OR SIDE IMPACT SENSOR IS ACCIDENTALLY DROPPED DURING SERVICE, THE MODULE OR SENSOR MUST BE SCRAPPED AND REPLACED WITH A NEW UNIT. FAILURE TO TAKE THE PROPER PRECAUTIONS COULD RESULT IN ACCIDENTAL AIRBAG DEPLOYMENT AND PERSONAL INJURY OR DEATH.

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 MCI 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 to ground. 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.