Diagnostic System Check

Circuit Description
The ignition switch supplies the ignition 1 voltage to the Inflatable Restraint Sensing and Diagnostic Module (SDM) at terminal 3 using the SIR Fuse. The ignition switch also supplies ignition 1 voltage to the instrument cluster. When the ignition switch is first turned to the RUN position, the instrument cluster responds by flashing the AIR BAG warning lamp 7 times. The SDM performs tests on the SIR system while the instrument cluster is flashing the warning lamp. If the SDM detects no malfunctions, the SDM commands the Instrument Panel Cluster (IPC) to turn the warning lamp OFF. If the SDM detects a malfunction, the SDM commands the IPC in order to turn the warning lamp ON. If the instrument cluster receives no message from the SDM, the instrument cluster will turn the warning lamp ON.

Diagnostic Aids
Ensure that you diagnose the diagnostic trouble codes in the order specified by the SIR Diagnostic System Check. Failure to do so may result in the following conditions:
^ Extended diagnostic time.
^ Incorrect diagnosis.
^ Incorrect parts replacement.

If the AIR BAG warning lamp does not flash 7 times when the ignition switch is turned to RUN, then the instrument cluster is not operating correctly. If a State Of Health (SOH) DTC is present, refer to the diagnostic aids for that specific SOH DTC.

Test Description
The numbers below refer to the step numbers on the diagnostic table.
1. This test checks for scan tool communication with SDM module on the Serial Data Line.
2. This test checks for scan tool communications with other modules on the Serial Data Line.
3. This test refers to the appropriate DTC Table and Diagnostic Aids for diagnosis of the current and/or history DTCs.
4. The AIR BAG warning lamp should flash seven times after the ignition switch is first turned to the RUN position.
5. The AIR BAG warning lamp indicates improper operation.