SIR Diagnostic System Check

The diagnostic procedures are designed to find and repair SIR malfunctions. To get the best results, it is important to use the diagnostic charts and follow the sequence listed below:

A. PERFORM THE "SIR DIAGNOSTIC SYSTEM CHECK."
The "SIR Diagnostic System Check" must be the starting point of any SIR diagnostics. The "SIR Diagnostic System Check" checks for proper "AIR BAG" warning lamp operation, the ability of the DERM to communicate through the data link connector, and whether SIR diagnostic trouble codes exist.
B. REFER TO THE PROPER DIAGNOSTIC CHART AS DIRECTED BY THE "SIR DIAGNOSTIC SYSTEM CHECK."
The "SIR Diagnostic System Check" will lead you to the correct chart to diagnose any SIR malfunctions. Bypassing these procedures may result in extended diagnostic time, incorrect diagnosis and incorrect parts replacement.
C. REPEAT THE "SIR DIAGNOSTIC SYSTEM CHECK" AFTER ANY REPAIR OR DIAGNOSTIC PROCEDURES HAVE BEEN PERFORMED.

Performing the "SIR Diagnostic System Check" after all repair or diagnostic procedures will ensure that the repair has been made correctly and that no other fault conditions exist.

CIRCUIT DESCRIPTION
When the ignition switch is first turned "ON" (Run) system voltage is applied from the AIR BAG Fuse to the DERM at the "Ignition 1" input terminals "A3" and "B3" and from the GAUGES fuse to the DERM at the "SIR Indicator High" input. The DERM responds by flashing the "AIR BAG" warning lamp 7 to 9 times while performing tests on the SIR system.

When the engine is being cranked, system voltage is applied from the RLC fuse to the DERM at the "Crank" input.

The DERM responds by grounding the "SIR Indicator Low" output until system voltage is removed from the "Crank" input. This results in the "AIR BAG" warning lamp being "ON" steady during cranking.

After cranking the DERM will again flash the "AIR BAG" warning lamp 7 to 9 times and perform tests on the SIR system.

NOTES ON SYSTEM CHECK CHART
1. The AIR BAG" warning lamp should flash 7 to 9 times after ignition is first turned "ON."
2. The "AIR BAG" warning lamp should remain "ON" steady during cranking.
3. After cranking, the "AIR BAG" warning lamp should flash 7 to 9 times then go "OFF."
4. The "AIR BAG" warning lamp has successfully completed the "Bulb Check."
5. This test checks for the proper operation of the "Serial Data" circuit. This test will also determine whether history diagnostic trouble codes are stored and what these diagnostic trouble codes are.
6. Improper operation of the "AIR BAG" warning lamp is indicated. This test differentiates a warning lamp stays "ON" condition from a warning lamp does not come "ON" condition.
7. This test differentiates a current diagnostic trouble codes exist condition from a diagnostics enabled when not requested condition.
8. The "AIR BAG" warning lamp has completed the "Bulb Check" and indicates current diagnostic trouble codes exist.
9. This test checks for proper operation of the "Serial Data" circuit. This test will also indicate what diagnostic trouble codes are stored and whether they are current or history.

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