Air Bag Control Module: Description and Operation

The inflatable restraint sensing and diagnostic module (SDM) performs the following functions in the SIR system:
^ Energy Reserve - The SDM maintains 23 Volt Loop Reserve (23 VLR) energy supplies to provide deployment energy for the frontal air bags. Ignition voltage can provide deployment energy if the 23 Volt Loop Reserves malfunction.
^ Crash Detection
- Frontal - The SDM monitors vehicle velocity changes in order to detect frontal crashes that are severe enough to warrant deployment of the frontal air bags.
- Side Impact - The SDM monitors vehicle velocity changes along with SIS information in order to detect side impact crashes that are severe enough to warrant deployment of the side air bags.
^ Air Bag Deployment
- Frontal - 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.
- Side - During a side impact crash of sufficient force, the SDM will cause enough current to flow through one of the side inflator modules to deploy that side air bag.
^ Seat Belt Pretensioner Crash Detection - The SDM monitors vehicle velocity changes in order to detect frontal crashes that are severe enough to warrant deployment of the seat belt pretensioners.
^ Seat Belt Pretensioner Deployment - During a frontal crash of sufficient force, the SDM will cause enough current to flow through the pretensioners, deploying the pretensioners.
^ Frontal and Side Crash Recording - The SDM records information regarding the SIR system status during a frontal crash or a side crash.
^ Side Impact System Malfunction Monitoring - The SDM monitors a diagnostic line from each inflatable restraint Side Impact Sensors (SIS). Both SISs communicate the status of the side impact air bag system to the SDM.
^ 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 (DTCs) 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 warning lamp.

The SDM connects to the SIR wiring harness using a 34-way connector. The SDM receives power whenever the ignition switch is ON.