Diagnosis & Repair
- Check for spark at misfiring cylinder. See IGNITION CHECKS in BASIC DIAGNOSTIC PROCEDURES article. If spark is present, go to next step. If spark is not present, go to step 4.
- Check for open or short in IGF and IGT circuits between ECM E14 connector and suspect coil/ignitor. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If circuits are okay, go to next step.
- Disconnect suspect ignition coil/ignitor connector. Turn ignition on. Backprobing, measure voltage between ground and terminals No. 27 (Yellow/Black wire) and No. 28 (Yellow wire) at ECM E14 connector. See Figure. If voltage is 4.5-5.5 volts, replace suspect ignition coil/ignitor. If voltage is not 4.5-5.5 volts, replace ECM and retest.
- Check for open or short in IGT circuit between ECM E14 connector and suspect ignition coil/ignitor. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If circuit is okay, go to next step.
- If using an oscilloscope, go to next step. If not using an oscilloscope, access ECM behind glove box. Backprobing, measure voltage between ground and each IGT circuit terminal at ECM E14 connector while cranking engine. See IDENTIFYING IGT CIRCUIT ECM E14 CONNECTOR TERMINALS table. If voltage is .1-4.5 volts, go to step 7. If voltage is not .1-4.5 volts, replace ECM and retest.
- Backprobing, connect oscilloscope between terminal No. 17 (White/Black wire) ECM E13 connector and each IGT circuit terminal at ECM E14 connector. See IDENTIFYING IGT CIRCUIT ECM E14 CONNECTOR TERMINALS table. Crank engine or allow engine to idle. Waveforms should be as illustrated. See Fig 1. If waveforms are as illustrated, go to next step. If waveforms are not as illustrated, replace ECM and retest.
- Disconnect all ignition coil connectors. Backprobing, measure voltage between ground and each IGT circuit terminal of ECM E14 connector while cranking engine. See IDENTIFYING IGT CIRCUIT ECM E14 CONNECTOR TERMINALS table. If voltage is .1-4.5 volts, go to next step. If voltage is not .1-4.5 volts, replace ECM and retest.
- Disconnect suspect ignition coil/ignitor connector. Measure voltage between ground and suspect coil/ignitor harness connector terminal No. 1 (Black/Red wire). Turn ignition switch to ON position, then to START position. If voltage is not 9-14 volts, repair ignition coil/ignitor power source circuit. If voltage is 9-14 volts, go to next step.
- Check for open White/Black wire between suspect ignition coil/ignitor connector terminal No. 4 and ground. Repair as necessary. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If circuit is okay, go to next step.
- Check EFI main relay. See appropriate SYSTEM & COMPONENT TESTING article. Replace EFI relay as necessary. If EFI main relay is okay, replace suspect ignition coil/ignitor.
IDENTIFYING IGT CIRCUIT ECM E14 CONNECTOR TERMINALS
| Circuit (Terminal No.) | Wire Color |
|---|---|
| IGT1 (11) | Green |
| IGT2 (12) | Black |
| IGT3 (13) | Blue |
| IGT4 (14) | Red |
| IGT5 (15) | Green |
| IGT6 (16) | Red/Blue |
| IGT7 (25) | Yellow/Green |
| IGT8 (26) | Black/White |