Initial Inspection and Diagnostic Overview

The diagnostic procedures are designed to find and repair SIR problems. 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 "INFL REST" warning lamp operation, the ability of the DERM to communicate through the data line, and whether SIR 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 problems. 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 or Bulb Test), system voltage is applied from fuse As to the DERM at the "Ignition 1" input terminals "A3" and "B3" and from fuse A9 to the DERM at the "SIR Indicator High" input. The DERM responds by flashing the "INFL REST" warning lamp 7 to 9 times.

When the engine is being cranked, system voltage is applied from fuse A11 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 "INFL REST" warning lamp being "ON" steady during cranking.

After cranking, the DERM will again flash the "INFL REST" warning lamp 7 to 9 times.

NOTES ON SYSTEM CHECK CHART
1. The "INFL REST" warning lamp should flash 7 to 9 times after ignition is first turned "ON".
2. The "INFL REST" warning lamp should remain "ON" steady during cranking.
3. Improper operation of the "INFL REST" warning lamp is indicated. This test differentiates a warning lamp stays "ON" condition from a warning lamp does not come "ON" condition.
4. After cranking, the "INFL REST" warning lamp should flash 7 to 9 times then go "OFF".
5. The "INFL REST" warning lamp has successfully completed the "Bulb Check." No current codes exist.
6. The "INFL REST" has completed a "Bulb Check" and indicates current codes exist.

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