System Description

AIRBAG SYSTEM/OCCUPANT RESTRAINT CONTROLLER SYSTEM
The 2001 Airbag System contain the following components: Occupant Restraint Controller (ORC), Airbag Warning Indicator, Clockspring, Driver and Passenger Dual Squib Airbags, Seat belt Tensioners, Left and Right Side Impact Airbag Control Module (SIACM), and Curtain (roof mounted) Airbags.

The (ORC) is a new type of Airbag Control Module (ACM) that supports staged airbag deployment. 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. The ORC has four major functions: PCI Bus communications, On-board diagnostics, impact sensing, and component deployment. The ORC 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 ORC is secured to the floor panel transmission tunnel between the front seats inside the vehicle. The ORC cannot be repaired or adjusted and must be replaced.

The ORC sends and/or receives PCI Bus messages with the Instrument Cluster (MIC), Body Control Module (BCM), Left and Right Side Impact Airbag Control Module (SIACM) and Powertrain Control Module (PCM). Diagnostic trouble codes will be set if the communication with these modules is lost or contains invalid information.

The microprocessor in the ORC monitors the impact sensor signal and the airbag system electrical circuits to determine the system readiness. The ORC also monitors bus messages from both SIACM. If the ORC detects a monitored system fault or SIACM fault, it sends a message to the instrument cluster via PCI bus to turn on the airbag warning indicator. The ORC can set both active and stored diagnostic trouble codes to aid in the diagnosing system problems. See ORC/SIACM DIAGNOSTIC TROUBLE CODES.

The ORC 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 ORC microprocessor determines when the deceleration rate is severe enough to require airbag system protection. The ORC also uses the crash severity to determine the level of driver and front passenger deployment, low medium or high. When the programmed conditions are met, the ORC sends an electrical signal to deploy the appropriate airbag system components.

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. 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 lamp 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 on, it means that the ORC 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.

SIDE IMPACT AIRBAG CONTROL MODULE (SIACM)
Supplemental driver and passenger curtain airbags provide side impact protection for the occupants. Each side airbag has it's own side impact airbag control module (SIACM) to provide independent impact sensing and deployment. SIACM are located on the left and right B post just above the seat belt retractor. One, same part number, SIACM is used on both side of the vehicle. However, for proper PCI bus operation each SIACM must have a unique module identification. To provide the unique module identification for both, left and right, the SIACM software looks for a ground on cavity # 5 of the SIACM connector. If cavity # 5 is grounded the SIACM communicates as a left SIACM otherwise it communicates as a right SIACM. The SIACM performs self diagnostics and circuit tests to determine if the system is functioning properly. If the test finds a problem the SIACM will set both active and stored diagnostic trouble codes. If a DTC is active the SIACM will request that the airbag warning lamp be turned on. The results of the system test are transmitted on the PCI Bus to the ORC once each second or on change in lamp state. If the warning lamp status message from the either SIACM contains a lamp on request, the ORC will set an active DTC. At the same time as the DTC is set, the ORC sends a PCI Bus message to the (MIC) requesting the airbag warning indicator be turned on. Observe all ORC warning and caution statements when servicing or handling the SIACM. SIACM are not repairable and must be replaced if they are dropped.

WARNING: THE AIRBAG SYSTEM IS 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. 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 lamp 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 MIC performs a lamp check by turning the airbag warning indicator on for 6 - 8 seconds. After the lamp check, if the indicator turns on, it means that the ORC 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.