ECM Power Supply & Ground Tests
- Check Main Relay - Turn ignition on and off. Listen for operating (clicking) sounds from main relay. If clicking is heard, go to step 3). If clicking is not heard, replace main relay.
- Check Harness Connector Of Main Relay Circuit - Turn ignition off. Disconnect main relay harness connector. Turn ignition on. Using DVOM connected to ground, check voltage to main relay harness connector terminals No. 2, 4 and 5. See appropriate wiring diagram in WIRING DIAGRAMS article. Voltage reading should be greater than 10 volts. If voltage reading is as specified, go to next step. If voltage reading is not as specified, check circuit between main relay and fuse block. If circuit is okay, 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, check voltage between ground and ECM harness connector terminals No. 2 and 13. Voltage reading should be at least 10 volts. If voltage reading is as specified, go to next step. If voltage reading is not as specified, check circuit between ECM and main relay.
- Check ECM Ground Circuit
- Turn ignition off. Disconnect ECM harness connector. Using DVOM, check resistance between chassis ground and the following ECM harness connector terminals:
- ECM 22-pin harness connector, Terminal Nos. 11 and 22.
- ECM 26-pin harness connector, Terminal Nos. 14, 15, 24 and 25.
Resistance on each listed terminal should be zero ohms. If resistance is as specified, see IGNITION CONTROL SYSTEM TESTS . If resistance is not as specified, check affected ground circuit between ECM harness connector or check for poor terminal contact in harness connector. See appropriate wiring diagram in WIRING DIAGRAMS article.