Side Impact Airbag Control Module (SIACM)

SIDE IMPACT AIRBAG CONTROL MODULE (SIACM)
Supplemental driver and front passenger seat airbags provide side impact protection for the front seat occupants. Each side airbag has it 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.

Both the left and right Side Impact Airbag Control Modules (SIACM) use the same part number. 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 ACM 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 ACM will set an active DTC. At the same time as the DTC is set, the ACM sends a PCI Bus message to the mechanical instrument cluster (MIC) requesting the Airbag Warning Lamp be turned on.

Observe all ACM 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 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 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 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.