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.

Use the diagnostic procedures in this service category to find 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:

1. Perform the SIR Diagnostic System Check. All SIR diagnostics must begin with the SIR Diagnostic System Check. The SIR Diagnostic System Check checks for proper AIR BAG warning lamp operation. The SIR Diagnostic System Check verifies the ability of the inflatable restraint Diagnostic Energy Reserve Module (DERM) to communicate through the data link connector. The SIR diagnostic system check determines whether SIR diagnostic trouble codes exist.
2. Refer to the diagnostic table as directed by the SIR Diagnostic System Check. The diagnostic tables will help enable you to diagnose any SIR system malfunction. Bypassing these procedures may result in the following:

•	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.

When you first turn ON the ignition switch, the AIR BAG fuse applies system voltage to the inflatable restraint Diagnostic Energy Reserve Module (DERM) at Ignition 1 input terminals A9 and A10. The GAUGE fuse also applies system voltage DERM at the Redundant Indicator Ignition 1 input terminal B2. The DERM then flashes the AIR BAG warning lamp seven times while performing tests on the SIR system.

During engine cranking, the CRANK fuse applies system voltage to the DERM at the Crank input terminal B10. The DERM then grounds the SIR Indicator output terminal B1 until the system voltage is removed from the Crank input. This results in the AIR BAG warning lamp coming on steady during cranking.

After cranking, the DERM flashes the AIR BAG warning lamp six times. The DERM also performs tests on the SIR system.

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:

Refer to step numbers on the diagnostic table.

1. The AIR BAG warning lamp should flash seven times after the ignition switch is turned ON.

2. The AIR BAG warning lamp should remain on steady during cranking.

3. After cranking, the AIR BAG warning lamp should flash six times, then go off.

4. This test checks for the proper operation of the Serial Data line. This test will also determine whether history DTCs are stored and, if so, identify them.

5. This test checks for the DERM's ability to communicate through the Serial Data Line.

6. This test refers to the appropriate DTC Table Diagnostic Aids for diagnosis of the history DTCs.

7. When the AIR BAG warning lamp flashes four times during BULB CHECK, this indicates a malfunction in the redundant lamp driver circuitry. These malfunctions are diagnosed by DTC B1062.

8. Improper operation of the AIR BAG warning lamp is indicated. This test differentiates a warning lamp that stays on condition from a warning lamp that does not come on condition.