Hombre XS Space Cab 2WD V6-4.3L (1998)
Sensing And Diagnostic Module: Description and Operation
The supplemental restraint Sensing and Diagnostic Module (SDM) performs the following functions in the SRS:
* Energy Reserve - The SDM maintains 23 Volt Loop Reserve (23 VLR) energy supplies to provide deployment energy. Ignition voltage can provide
deployment energy if the 23 Volt Loop Reserves malfunction.
* Frontal Crash Detection - The SDM monitors vehicle velocity changes to detect frontal crashes that are severe enough to warrant deployment.
* Air Bag Deployment - During a frontal crash of sufficient force, the SDM will cause enough current to flow through the inflator modules to deploy
the air bags.
* Frontal Crash Recording - The SDM records information regarding the SRS status during a frontal crash.
* Malfunction Detection - The SDM performs diagnostic monitoring of the SRS electrical components. Upon detection of a circuit malfunction, the
SDM will set a Diagnostic Trouble Code (DTC).
* Malfunction Diagnosis - The SDM displays SRS Diagnostic Trouble Codes and system status information through the use of a scan tool.
* Driver Notification - The SDM warns the vehicle driver of SRS malfunctions by controlling the AIR BAG warning lamp.
The SDM connects to the SRS wiring harness using a 12-way connection The SDM harness connector uses a shorting bar across certain terminals in the
contact area. Removal of the SDM Connector Position Assurance (CPA) or the harness connector itself will connect the AIR BAG warning lamp to
ground through the shorting bar.
The AIR BAG warning lamp will come ON steady with power applied to the SDM when either one of the following two conditions exist:
- You remove the SDM CPA.
- You disconnect the SDM harness connector. The SDM receives power whenever the ignition switch is in the RUN or START positions.
