System Operation

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 (23 VLR) energy supplies to provide deployment energy for the air bags. Ignition voltage can provide deployment energy if the 23 Volt Loop Reserves malfunction.
^ Crash Detection - The SDM monitors vehicle velocity changes in order to detect frontal crashes that are severe enough to warrant deployment.
^ 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 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 in the instrument cluster via Class 2 serial data.

The SDM connects to the SIR wiring harness using the following connector(s):

The 18-way connector provides power, ground, and all the required interfaces for the frontal air bag deployment loops.

The SDM receives power when the ignition switch is in the RUN position.