SIR Diagnostic System Check

Circuit Description
The ignition switch supplies 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 (IPC). When the ignition switch is first turned to the ON position, 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
You must diagnose the diagnostic trouble codes in the order specified by the SIR Diagnostic System Check. Failure to do so may result in the following:
^ Extended Diagnostic Time
^ Incorrect Diagnosis
^ Incorrect Parts Replacement
If the AIR BAG warning lamp does not flash seven times when the ignition switch is turned to the ON position, then the IPC is not operating correctly.
If a State Of Health (SOH) DTC is present, refer to Body Control Systems.

Test Description
Refer to step numbers on the diagnostic table.
1. The Instrument Cluster (IPC) should flash the AIR BAG warning lamp seven times after the ignition switch is first turned to the ON position.
2. The AIR BAG warning lamp should turn OFF after flashing seven times.
3. This test checks for the proper operation of the Class 2 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 Class 2 serial data line. This test also identifies any stored history diagnostic trouble codes.