Pcm Power & Ground Circuit
- Observe main relay (located in engine compartment relay/fuse block) while ignition is cycled on then off. See Fig 1. If sound is heard at relay, turn ignition off. Disconnect PCM harness connectors and go to step 6. If no sound is heard, go to next step.
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- Ensure ignition if off. Remove main relay. Measure resistance between relay terminals No. 3 and No. 4. See Fig 1. Resistance should be 70-110 ohms. If resistance is as specified, go to next step. If resistance is not as specified, replace relay.
- Check continuity between terminals No. 1 and No. 2. Continuity should not exist. Apply battery voltage to terminal No. 3 and ground to terminal No. 4. Continuity should exist between terminals No. 1 and No. 2. If continuity is not as specified, replace relay. If continuity is as specified, go to next step.
- Ensure LAMP fuse (60-amp) in engine compartment relay/fuse block is okay. If fuse is blown, check for short to ground and repair as necessary. If fuse is okay, go to next step.
- Turn ignition off. Install main relay. Disconnect PCM harness connectors. Check PCM harness connector E92, terminal No. 20 and PCM harness connector C21, terminals No. 2, No. 15 and No. 19 for proper contact. See Fig 2. If poor terminal contact is found, repair as necessary and retest system. If connection is okay, go to next step.
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- Turn ignition on. Measure voltage between ground and PCM harness connector E92, terminals No. 20 (Black/White wire) and No. 19 (Green wire). If readings are 10-14 volts on both circuits, go to next step. If readings are not 10-14 volts on both circuits, repair open in Black/White wire between LAMP fuse (60-amp) and main relay, or open in Green wire between main relay and PCM. Repair as necessary.
- Using a fused jumper wire, ground PCM harness connector C21, terminal No. 22 (Green wire). Turn ignition on. Measure voltage between ground and PCM harness connector C21, terminal No. 2 (Red/Black wire). If reading is 10-14 volts, go to next step. If reading is not 10-14 volts, repair open in Red wire between FI fuse (15-amp) and main relay, or open in Red/Black wire between PCM and main relay.
- Check for open in Black or Black/Orange wire (PCM ground wires). Repair as necessary. If wires are okay, replace PCM. Retest system.