Sensing & Diagnostic Module (SDM)
WARNING: This page is about a different car, the 2002 Buick Regal and 2002 Buick Century. However, it is still accessible from the selected car via links, so may be relevant.
SDM monitors vehicle velocity changes to detect frontal and side impact collisions which are severe enough to warrant air bag module deployment. When a collision of sufficient force is detected, SDM causes current to flow through air bag module deployment loops to deploy air bags. SDM also maintains a 36 Volt Loop Reserve (36 VLR) energy supply to provide deployment energy for up to one minute after loss of battery voltage.
Additionally, 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 system malfunctions by turning AIR BAG warning light on.