Caution: In order to avoid deploying the air bag when troubleshooting the SIR system, use only the equipment specified in this manual and the instructions given in this manual. Failure to use the specified equipment as instructed could cause air bag deployment, personal injury to you or someone else, or unnecessary SIR system repairs.

Caution: If any water enters the vehicle's interior up to the level of the carpet or higher and soaks the carpet, the sensing and diagnostic module (SDM) and the SDM harness connector may need to be replaced. The SDM could be activated when powered, which could cause deployment of the air bag(s) and result in personal injury. Before attempting these procedures, the SIR system must be disabled. Refer to Disabling the SIR System.

These diagnostic procedures will help you in order to find and repair SIR system malfunctions. This service category also contains information for repairing SIR system malfunctions. For best results, use the diagnostic tables, and follow the sequence listed below:

Important: All SIR diagnostics must begin with the SIR diagnostic system check.

1. Perform the SIR diagnostic system check. The SIR diagnostic system check determines the following items:

•	The proper AIR BAG warning lamp operation.

•	The ability of the SDM in order to communicate through the data link connector (DLC).

•	The existence of the SIR diagnostic trouble codes (DTC).

2. Refer to the diagnostic table as directed by the SIR diagnostic system check. The diagnostic tables will help enable you in order to diagnose any SIR system malfunction. Bypassing these procedures may result in the following conditions:

•	Extended diagnostic time

•	Incorrect diagnosis

•	Incorrect parts replacement

3. Repeat the SIR diagnostic system check after you perform any repair or diagnostic procedures. This will verify that you correctly performed the repair. This will also ensure that no other malfunctions exist.

The ignition switch supplies ignition positive voltage voltage to the inflatable restraint sensing and diagnostic module (SDM) at terminal 10 using the AIR BAG Fuse. When the ignition switch is first turned to the RUN position, the SDM responds by flashing the AIR BAG warning lamp 7 times, then turning the warning lamp OFF, while performing tests on the SIR system.

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:

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. This test differentiates a warning lamp stays ON condition or a warning lamp does not come ON condition.