SW2 L4-1.9L DOHC VIN 7 (1997)
Air Bag Control Module: Description and Operation
CAUTION: BE CAREFUL WHEN YOU HANDLE A SENSING AND DIAGNOSTIC MODULE (SDM).
DO NOT STRIKE OR JOLT THE SDM. BEFORE APPLYING POWER TO THE SDM:
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REMOVE ANY DIRT GREASE, ETC. FROM THE MOUNTING SURFACE.
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POSITION THE SDM HORIZONTALLY ON THE MOUNTING SURFACE.
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POINT THE ARROW ON THE SDM TOWARD THE FRONT OF THE VEHICLE.
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TIGHTEN ALL OF THE SDM FASTENERS AND SDM BRACKET FASTENERS TO THE SPECIFIED TORQUE VALUE.
FAILURE TO FOLLOW THE CORRECT PROCEDURES COULD CAUSE AIR BAG DEPLOYMENT, PERSONAL INJURY, OR
UNNECESSARY SIR SYSTEM REPAIRS.
NOTICE: Do not open the SDM case for any reason. Touching the connector pins or soldered components may cause electrostatic discharge damage.
Repair of a faulty SDM is by replacement only.
The sensing and diagnostic module (SDM) is designed to perform the following functions in the SIR system:
1. Frontal Crash Detection: The SDM monitors vehicle acceleration changes to detect frontal crashes which are severe enough to warrant
deployment.
2. Inflator Module Deployment: When a frontal crash requiring deployment is detected the SDM provides enough current to deploy the inflator
modules.
3. Energy Reserve: The SDM maintains approximately a 23 volt loop energy reserve (VLR) energy supply to provide deployment current if ignition
voltage is lost in a frontal crash.
4. Malfunction Detection: The SDM performs diagnostic monitoring of SIR system electrical components and sets diagnostic trouble codes when a
malfunction is detected.
5. Driver Notification: The SDM warns the driver of the SIR system malfunctions by controlling the AIR. BAG telltale lamp.
6. Malfunction Diagnosis: The SDM displays SIR diagnostic fault codes and system status information through a scan tool.
7. Crash Recording: The SDM records information regarding the SIR system status when deployment has been commanded.
The SDM is connected to the SIR wiring harness by a 12-way connector. This connector has a shorting bar across two terminals which connects the AIR
BAG telltale lamp to ground when the SDM connector is disconnected. This will cause the AIRBAG telltale to come "On" steady whenever the ignition
switch is at the RUN or START positions with the SDM disconnected.
