Cavalier L4-2.2L VIN 4 (1998)
Air Bag Control Module: Description and Operation
The inflatable restraint Sensing and Diagnostic Module (SDM) performs the following functions in the SIR system:
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Energy Reserve - The SDM maintains 23 Volt Loop Reserve (23 VLR) energy supplies to provide deployment energy. Ignition voltage can
provide deployment energy if the 23 Volt Loop Reserves malfunction.
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Frontal Crash Detection - The SDM monitors vehicle velocity changes to detect frontal crashes that are severe enough to warrant deployment.
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Air Bag Deployment - During a frontal crash of sufficient force, the SDM will cause enough current to flow through the inflator modules to
deploy the air bags.
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Frontal Crash Recording - The SDM records information regarding the SIR system status during a frontal crash.
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Malfunction Detection - The SDM performs diagnostic monitoring of the SIR system electrical components. Upon detection of a circuit
malfunction, the SDM will set a Diagnostic Trouble Code (DTC).
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Malfunction Diagnosis - The SDM displays SIR Diagnostic Trouble Codes and system status information through the use of a scan tool.
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Driver Notification - The SDM warns the vehicle driver of SIR system malfunctions by controlling the AIR BAG warning lamp.
The SDM connects to the SIR wiring harness using a 12-way connector. If this connector is removed from the SDM, the UART data link is broken and
the Instrument Panel Cluster (IPC) will turn the AIR BAG warning lamp ON steady whenever the ignition switch is in the RUN or START positions.
