Terraza FWD V6-3.5L VIN 8 (2005)
Air Bag Control Module: Description and Operation
INFLATABLE RESTRAINT SENSING AND DIAGNOSTIC MODULE (SDM)
The sensing and diagnostic module (SDM) is a microprocessor and the control center for the supplemental inflatable restraint (SIR) system. The SDM
contains internal sensors along with several external sensors, if equipped, mounted at strategic locations on the vehicle. In the event of a collision, the
SDM compares the signals from the internal and external sensors to a value stored in memory. When the generated signals exceed the stored value, the
SDM will cause current to flow through the appropriate deployment loops to deploy the air bags. The SDM records the SIR system status when a
deployment occurs and turns the AIR BAG indicator located in the instrument panel cluster (IPC) ON. The SDM performs continuous diagnostic
monitoring of the SIR system electrical components and circuitry when the ignition is turned ON. If the SDM detects a malfunction, a DTC will be
stored and the SDM will command the AIR BAG indicator ON, notifying the driver that a malfunction exist. In the event that ignition positive voltage is
lost during a collision, the SDM maintains a 23-volt loop reserve (23 VLR) for deployment of the air bags. It is important when disabling the SIR system
for servicing or rescue operations to allow the 23 VLR to dissipate, which could take up to 1 minute.
