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:

• Wiring harness circuit (MIL).
• Faulty Powertrain Control Module (PCM).

Fig 1: MIL Circuit Schematic

1. Step 1) MIL Always On  Perform KOEO SELF-TEST . If any trouble codes are present, service as necessary before continuing. If no trouble codes are present, turn ignition off. Disconnect PCM 104-pin connector. Inspect pins for damage. Install EEC-V Breakout Box (014-00950), leaving PCM disconnected. Measure and record resistance between test pins No. 2 and No. 51 and 103 (PWR GND). If resistance is less than 5 ohms, repair short circuit between test pin No. 2 and MIL. If resistance is 5 ohms or more, replace PCM.
2. Step 2) MIL Does Not Come On  Turn ignition on. Measure voltage between ground side of MIL fuse and negative battery terminal. 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. Step 3) Check For B+ At Fuse  Leave ignition on. Measure voltage between positive side of MIL fuse and negative battery terminal. If voltage is 10.5 volts or less, repair open in MIL or B+ circuit. If voltage is more than 10.5 volts, replace MIL fuse.
4. Step 4) Check For B+ At MIL Bulb  Leave ignition on. Measure voltage between instrument cluster connector terminal B+ and negative battery terminal. If voltage is 10.5 volts or less, repair open in fuse, MIL bulb or B+ circuit. If voltage is more than 10.5 volts, go to next step.
5. Step 5) Check Continuity Of MIL Circuit  Turn ignition off. Measure resistance between instrument cluster connector MIL terminal and test pin No. 2 of breakout box. If resistance is less than 5 ohms, replace PCM. If MIL is still on, fault is in instrument cluster. If resistance is 5 ohms or more, repair open in MIL circuit.