Sensing & Diagnostic Module (SDM)
WARNING: This page is about a different car, the 2002 Oldsmobile Aurora. However, it is still accessible from the selected car via links, so may be relevant.
SDM monitors vehicle velocity changes to detect frontal or side impacts which are severe enough to warrant SIR system deployment. When a frontal or side impact of sufficient force is detected, SDM causes current to flow through applicable air bag modules, causing air bag module deployment. SDM maintains a 23 Volt Loop Reserve (23 VLR) energy supply to provide deployment energy for up to one minute after loss of ignition voltage.
SDM provides diagnostic monitoring of SIR system electrical components. When a malfunction is detected, SDM sets a Diagnostic Trouble Code (DTC) which can be retrieved using a scan tool. SDM warns driver of SIR system malfunctions by controlling AIR BAG warning light.