Sensing And Diagnostic Module (SDM)
WARNING: This page does not describe the selected car, but rather 9 other vehicles, including the 1996 GMC Vandura Special, 1996 GMC Vandura, 1996 GMC Savana Special, 1996 GMC Savana Camper Special, and 1996 GMC Savana. However, it is still accessible from the selected car via links, so may be relevant.
The SDM monitors vehicle velocity changes to detect frontal crashes which are severe enough to warrant air bag module deployment. When a frontal crash of sufficient force is detected, SDM will cause enough current to flow through air bag modules to deploy air bag modules. The SDM also maintains a 23 Volt Loop Reserve (23 VLR) energy supply to provide deployment energy in cases where ignition voltage is lost in a frontal crash.
Additionally, the SDM provides diagnostic monitoring of the SIR system electrical components. When a malfunction is detected, the SDM sets a diagnostic trouble code (DTC) which is retrieved using a scan tool. The SDM warns the driver of system malfunctions by controlling the AIR BAG warning light.