K 2500 Yukon 4WD V8-6.0L VIN U (2000)
Inflatable Restraint Sensing and Diagnostic Module: Description and Operation
The inflatable restraint Sensing and Diagnostic Module (SDM) performs the following functions in the SIR system:
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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.
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Frontal Crash Detection - The SDM monitors vehicle velocity changes to detect frontal crashes that are severe enough to warrant air bag
deployment. The SDM also monitors the front end discriminating sensor which provides an input the to the SDM to further support air bag
deployment.
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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.
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Frontal Crash Recording - The SDM records information regarding the SIR system status during a frontal crash.
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Side Impact Crash Detection - The SDM communicates with both inflatable restraint Side Impact Sensors (SIS) and monitors the vehicle side
accelerations/decelerations to determine if during a side crash event side air bag protection is needed for the Driver and/or Passenger.
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Side Air Bag Deployment - During a side impact crash of sufficient force, the SDM will cause enough current to flow through the side inflator
modules to deploy the side air bags.
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Side Impact Crash Recording - The SDM records information regarding the SIR system status during a side impact crash.
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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).
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Malfunction Diagnosis - The SDM displays SIR Diagnostic Trouble Codes (DTC) and system status information through the use of a scan
tool.
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Driver Notification - The SDM warns the vehicle driver of SIR system malfunctions by controlling the AIR BAG warning lamp. The SDM
sends a message over the Class 2 serial data line requesting to turn ON the AIR BAG warning lamp.
The SDM connects to the SIR wiring harness using a yellow 18-way connector and a.yellow 8-way connector.
The SDM receives power whenever the ignition switch is in the RUN or START positions.
