Airbag System: Notes

The 2004 CS Airbag System contains the following components:

Occupant Restraint Controller (ORC)
Airbag Warning Indicator
Clockspring
2-stage Driver and Passenger Airbags
Driver Knee Blocker Airbag
Left and Right Curtain Airbags
Left and Right Front Impact Sensors
Three (3) Left impact Sensors
Three (3) Right impact Sensors
Driver and Passenger Seat Belt Tensioners

The Occupant Restraint Controller (ORC) is also referred to as an Airbag Control Module (ACM). The ACM has four major functions: onboard diagnostics, PCI Bus communications, impact sensing and squib deployment. The Airbag Warning Indicator in the Instrument Cluster is the only point at which the customer can observe symptoms of a system malfunction.

The microprocessor in the ACM monitors the internal and external airbag system electrical circuits to determine the system readiness. When a monitored system is determine out of range, the ACM microprocessor will set both active and stored diagnostic trouble codes to aid in the diagnosing system problems. See DIAGNOSTIC TROUBLE CODES in this section. 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 instrument panel. 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 Powertrain Control Module (PCM). Diagnostic trouble codes will be set if the communication with these modules is lost or contains invalid information. 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 via a PCI Bus message. 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 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. If the lamp remains on, there could be an active fault in the system or the MIC lamp circuit may be internally shorted.

The ACM uses two (2) Front Impact Sensors along with the ACM Accelerometer to sense the rate of vehicle deceleration, provide verification of the direction and severity of an impact. When the preprogrammed conditions are met, the ACM sends an electrical signal to deploy the appropriate front airbag system components. The ACM Accelerometer and the six (6) side impact sensors (three (3) Left and three (3) Right Impact Sensors) are used to provide verification of the direction and severity of a side impact. When the preprogrammed conditions are met, the ACM sends an electrical signal and deploys the appropriate Left or Right Curtain Air-bag.

Staged deployment is the ability to deploy one squib or both squibs in a dual squib airbag or a single curtain squib as needed to provide the appropriate restraint for the severity of the impact. The first stage deployed is both seat belt tensioners, the knee blocker airbag, and the 1st stage squib of the Driver and Passenger Airbags are the first stage of deployment. The second stage consists of all the 1st stage previously described and the 2nd stage squib of the Driver and Passenger Airbags.

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.