SIR Diagnostic System Check

Diagnostic Chart:

The diagnostic procedures used are designed to find and repair SIR system malfunctions. To get the best results, it is important to use the diagnostic tables 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 TABLE AS DIRECTED BY THE "SIR DIAGNOSTIC SYSTEM CHECK." The "SIR Diagnostic System Check" will lead you to the correct table to diagnose any SIR system malfunction. 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 no other malfunctions 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 "Ignition 1" input terminals "A9" and "A10" and from the "GAGES" fuse to the DERM at the "Redundant Indicator Ignition 1" input terminal "B2." The DERM responds by flashing the "AIR BAG" warning lamp seven times while performing tests on the SIR system.

When the engine is being cranked, system voltage is applied from the "CRANK" fuse to the DERM at the "Crank" input terminal "B10." The DERM responds by grounding the "SIR Indicator" output terminal "B1" 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 flash the "AIR BAG" warning lamp six times and perform tests on the SIR system.

NOTES ON SYSTEM CHECK TABLE
1. The "AIR BAG" warning lamp should flash seven times after the ignition switch 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 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 diagnostic trouble codes 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 for diagnosis of the history DTC's set to the memory in the DERM.
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 62 table.
8. 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.
9. This test checks for proper operation of the "Serial Data" line. This test will also identify the stored diagnostic trouble codes and whether they are current or history.
10. This test requests that you record all trouble codes on the repair order and then refers you to the appropriate DTC table for diagnosis of all DTC's.
11. This step refers you back to the beginning of the SIR DIAGNOSTIC SYSTEM CHECK to ensure the system is "OK" and functioning properly.

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.