Air Bag Control Module: Description and Operation

INFLATABLE RESTRAINT SENSING AND DIAGNOSTIC MODULE (SDM)

The SDM performs the following functions in the SIR system:
- Energy reserve - The SDM maintains a sufficient energy reserve to provide deployment energy for the frontal air bags.
- Frontal crash detection - The SDM monitors vehicle velocity changes to detect frontal crashes that are severe enough to warrant deployment.
- Frontal air bag deployment - During a frontal crash of sufficient force, the SDM will cause enough current to flow through the frontal inflator modules to deploy the frontal air bags.
- Seat belt pretensioner deployment - During a frontal crash of sufficient force, the SDM will cause current to flow through the seat belt pretensioners in order to cause deployment.
- Frontal crash recording - The SDM records information regarding the SIR system status during a frontal crash.
- Malfunction detection - The SDM performs diagnostic monitoring of the SIR system electrical components. Upon detection of a circuit malfunction, the SDM will set a Diagnostic Trouble Code (DTC).
- Malfunction diagnosis - The SDM displays SIR Diagnostic Trouble Codes and system status information through the use of a scan tool.
- Driver notification - The SDM warns the vehicle driver of SIR system malfunctions by controlling the AIR BAG indicator.
- Vehicle system shutdown - In the event of a deployment, the SDM sends serial data to advise various other vehicle systems to take appropriate shutdown action.

The SDM connects to the SIR wiring harness using a 50-way connector.

The SDM receives power whenever the ignition switch is in the ON or START positions.