L200 L4-2.2L VIN F (2002)
Inflatable Restraint Sensing And Diagnostic Module: Description and Operation
SENSING AND DIAGNOSTIC MODULE (SDM)
The SIR control module that provides reserve energy to the deployment loop(s) to deploy the air bag when required, and performs diagnostic monitoring
of all SIR system components.
The SDM is designed to perform the following functions in the SIR system:
1. Energy Reserve: The SDM maintains approximately a 23 volt Loop Reserve (VLR) energy supply to provide deployment current if ignition
voltage is lost in a frontal crash.
2. Frontal Crash Detection: The SDM monitors vehicle acceleration changes to detect frontal crashes Which are severe enough to warrant
deployment.
3. Side Crash Detection: The SDM monitors vehicle velocity changes, along with SIS information, to detect side impact crashes Which are severe
enough to warrant deployment.
4. Inflator Module Deployment: When a crash requiring deployment is detected, the SDM provides enough current to the frontal or a side inflator
module(s) to deploy the air bag(s).
5. Frontal Crash Recording: The SDM monitors information regarding the SIR system status when deployment has been commanded.
6. Side Impact System Malfunction Monitoring: The SDM monitors the SIS. The SIS can communicate the status of the side impact air bag system.
7. Malfunction Detection: The SDM performs diagnostic monitoring of SIR system electrical components and sets Diagnostic Trouble Codes
(DTCs) when a malfunction is detected.
8. Malfunction Diagnosis: The SDM displays SIR Diagnostic Trouble Codes (DTCs) and system status information through a Scan tool.
9. Driver Notification: The SDM warns the driver of SIR system malfunctions by controlling the AIR BAG telltale.
The SDM is connected to the SIR wiring harness by an 18-way connector and an 8-way side air bag connector. The SDM receives power whenever the
ignition is On.
