Air Bag Control Module: Description and Operation

INFLATABLE RESTRAINT SENSING AND DIAGNOSTIC MODULE (SDM)

The SDM performs the following functions in the SIR system:
- Energy Reserve - The SDM maintains 12-16 Volt Loop Reserve (VLR) energy supplies to provide deployment energy for the frontal air bags. Ignition voltage can provide deployment energy if the 12-16 Volt Loop Reserves malfunction.
- Frontal Crash Detection - The SDM monitors vehicle velocity changes to detect frontal crashes that are severe enough to warrant deployment.
- Frontal Air Bag Deployment - During a frontal crash of sufficient force, the SDM will cause enough current to flow through the frontal inflator modules to deploy the frontal air bags.
- Seat Belt Pretensioner Deployment - During a frontal crash of sufficient force, the SDM will cause current to flow through the seat belt pretensioners in order to cause deployment.
- Frontal Crash Recording - The SDM records information regarding the SIR system status during a frontal crash.
- Side Impact System Malfunction Monitoring - The SDM monitors a diagnostic line from each inflatable restraint side impact sensor (SIS). Both SIS's communicate the status of the side impact air bag system to the SDM.
- Side Air Bag Deployment - During a side crash of sufficient force, the SDM will cause enough current to flow through one of the side inflator modules to deploy the side air bag.
- 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).
- Malfunction Diagnosis - The SDM displays SIR Diagnostic Trouble Codes and system status information through the use of a scan tool.
- Driver Notification - The SDM warns the vehicle driver of SIR system malfunctions by controlling the AIR BAG indicator.

The SDM connects to the SIR wiring harness using 28 --way and 2 12--way connectors.

The SDM receives power whenever the ignition switch is in the ON or START positions.