SIR Diagnostic System Check

CIRCUIT DESCRIPTION

When the ignition switch is first turned to RUN, Ignition 1 voltage is applied from the Sensing and Diagnostic Module (SDM) Fuse to the inflatable restraint Sensing and Diagnostic Module (SDM) at the Ignition 1 input, terminal 3. Ignition 1 is also applied to the Instrument Panel Cluster (IPC). The IPC responds by flashing the AIR BAG warning lamp seven times. The SDM performs tests on the SIR system while the IPC is flashing the warning lamp. If the SDM detects no malfunctions, the SDM commands the IPC to turn the warning lamp OFF. If the SDM detects a malfunction, the SDM commands the IPC to turn the warning lamp ON. If the IPC receives no message from the SDM, the IPC will turn the warning lamp ON.

DIAGNOSTIC AIDS
The order in which diagnostic trouble codes are diagnosed is very important. Failure to diagnose the DTCs in the order specified may result in extended diagnostic time, incorrect diagnosis and incorrect parts replacement.

If the AIR BAG warning lamp does not flash seven times when the ignition switch is turned to RUN, then the Instrument Panel Cluster (IPC) is not operating correctly.

If the scan tool cannot communicate with the SDM, then the Serial Data Line Class 2 may be damaged.

If (a) State Of Health (SOH) DTC(s) other than DTC U 1096 is (are) present, refer to the Diagnostic Aids for that specific SOH DTC in this section.

NOTES ON SYSTEM CHECK TABLE

Numbers below refer to step numbers on the diagnostic table.
1. The Instrument Panel Cluster (IPC) should flash the AIR BAG warning lamp seven times after the ignition is first turned to RUN.
2. After the AIR BAG warning lamp flashes seven times it should turn OFF.
3. This test checks for proper operation of the Serial Data line.
5. This test will identify the stored diagnostic trouble codes and whether they are current or history.
6. This test checks for the proper operation of the Serial Data line. This test will also determine whether history diagnostic trouble codes are stored and, if so, identify them.