Diagnostic Aids

Perform this test when instructed during QUICK TEST or if directed by other test procedures. This test is used to diagnose the following:

NOTE: If vehicle will not start, go to TEST A, step 1).

NOTE: Steps 1)- 5) are performed when directed here from WARNING INDICATOR LIGHTS under SYMPTOMS in TROUBLE SHOOTING - NO CODES article.

1) MIL Always On: Check MIL Circuit For Shorts To GND In Harness
If any KOEO or Continuous Memory DTCs are present, service DTCs before continuing. If no DTCs are present, turn ignition switch to OFF position. Disconnect PCM connector. Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Using a DVOM, measure resistance between PCM harness connector terminals No. 2 (MIL) and PWR GND and SIG RTN circuit terminals. See PCM PWR GND, SIG RTN & VREF TERMINAL IDENTIFICATION table. See Figure. If resistance is 10 k/ohms or less, repair MIL circuit for short to PWR GND or SIG RTN circuit between PCM and MIL. If resistance is 10 k/ohms or more, replace PCM.

NOTE: If vehicle will not start, go to TEST A, step 1).

2) MIL Never On
Turn ignition switch to ON position. Using a DVOM, measure voltage between negative battery terminal and output side of MIL fuse. If voltage is 10.5 volts or less, go to next step. If voltage is more than 10.5 volts, go to step 4).

3) Check For B+ Voltage To MIL Fuse

Using a DVOM, measure voltage between negative battery terminal and B+ side of MIL fuse. If voltage is 10.5 volts or less, repair open in B+ circuit to MIL fuse. See POWER DISTRIBUTION article in WIRING DIAGRAMS article. If voltage is more than 10.5 volts, replace MIL fuse. Recheck MIL operation.

4) Check B+ Circuit Voltage At Instrument Cluster

Turn ignition switch to OFF position. Disconnect instrument cluster connector. Refer to appropriate INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT. Turn ignition switch to ON position. Using a DVOM, measure voltage of B+ circuit between negative battery terminal and instrument cluster harness connector. If voltage is more than 10.5 volts, go to next step. If voltage is 10.5 volts or less, repair open in instrument cluster fuse or B+ circuit to instrument cluster. See appropriate INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT. Recheck MIL operation.

5) Check For Open In MIL Circuit Between PCM and Instrument Cluster

Turn ignition switch to OFF position. Disconnect PCM connector. Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Using a DVOM, measure resistance of MIL circuit between PCM harness connector terminal No. 2 and MIL terminal at instrument cluster harness connector. See Figure. If resistance is 5 ohms or more, repair open in MIL circuit. Recheck MIL operation. If resistance is less than 5 ohms, check MIL bulb and instrument cluster. See appropriate INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT. Repair as necessary. If no problems are found, replace PCM. Recheck MIL operation.