ECM Power Supply & Ground Tests
- Check Main Relay - Turn ignition off and remove main relay. Connect battery voltage to main relay terminals No. 1 and 2. Check resistance between main relay terminals No. 3 and 5, and terminals No. 4 and 6. See appropriate wiring diagram in WIRING DIAGRAMS article. Resistance should be less than 10 ohms in both tests. If resistance is as specified, go to next step. If resistance is not as specified, replace main relay.
- Check ECM Power Supply Circuit - Turn ignition off. Reconnect main relay harness connector. Disconnect ECM harness connector. Turn ignition on. Using DVOM, measure power supply between ECM connector terminals No. 1, 2 and 39 and terminal No. 19. If voltage is less than 10 volts, repair harness of power supply circuit. If voltage is more than 10 volts, check ECM ground circuit.
- Check ECM Ground Circuit
- Turn ignition off. Using DVOM, check resistance between chassis ground and the following ECM harness connector terminals:
- Terminal No. 11
- Terminal No. 17
- Terminal No. 18
- Terminal No. 19
- Terminal No. 20
- Terminal No. 42
- Terminal No. 46
- Terminal No. 69
- Terminal No. 94
Resistance on each listed terminal should be less than 5 ohms. If resistance is as specified, see IGNITION CONTROL SYSTEM TESTS . If resistance is not as specified, check affected ground circuit to ECM harness connector or check for poor terminal contact in harness connector. See appropriate wiring diagram in WIRING DIAGRAMS article.