Inflatable Restraint Sensing and Diagnostic Module (SDM)

The inflatable restraint Sensing and Diagnostic Module (SDM) performs the following functions in the SIR system:
^ Energy Reserve-The SDM maintains 23 Volt Loop Reserve (23VLR) energy supplies to provide deployment energy. Ignition voltage can provide deployment energy if the 23 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.
^ Frontal Crash Recording-The SDM records information regarding the SIR system status during a frontal crash.
^ 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 (DTC) 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 warning lamp. The SDM sends a message over the Class 2 serial data line requesting to turn ON the AIR BAG warning lamp.

The SDM connects to the SIR wiring harness using a yellow 18-way connector.

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