Rainier AWD L6-4.2L VIN S (2005)
Air Bag Control Module: Description and Operation
Sensing and Diagnostic Module (SDM)
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 various locations on the vehicle. In the event of a collision, the
SDM performs calculations using the signals received from the internal and external sensors. The SDM compares the results of the calculations to values
stored in memory. When these calculations 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 requests the instrument panel cluster (IPC) to turn the AIR
BAG indicator 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 request the IPC to turn the AIR BAG indicator ON. In the event
that ignition 1 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 to
note, when disabling the SIR System for servicing or rescue operations to allow the 23 VLR to dissipate, which could take up to 1 minute.
