DTC Troubleshooting

DTC Troubleshooting: P0118

DTC P0118: ECT Sensor 1 Circuit High Voltage

NOTE: Before you troubleshoot, record all freeze data and any on-board snapshot, and review the general troubleshooting information. Initial Inspection and Diagnostic Overview

1. Turn the ignition switch to ON (II).

2. Check ECT SENSOR 1 in the DATA LIST with the HDS.

Is about -40 °F (-40 °C) or less, or 4.92 V or more indicated?
YES - Go to step 3.

NO - Intermittent failure, the system is OK at this time. Check for poor connections or loose terminals at ECT sensor 1 and the ECM.


3. Turn the ignition switch to LOCK (0).

4. Disconnect the ECT sensor 1 2P connector.

5. Connect ECT sensor 1 2P connector terminals No. 1 and No. 2 with a jumper wire.

6. Turn the ignition switch to ON (II).

7. Check ECT SENSOR 1 in the DATA LIST with the HDS.

Is about -40 °F (-40 °C) or less, or 4.92 V or more indicated?
YES - Go to step 8.

NO - Go to step 20.






8. Turn the ignition switch to LOCK (0).

9. Remove the jumper wire from the ECT sensor 1 2P connector.

10. Turn the ignition switch to ON (II).

11. Measure the voltage between ECT sensor 1 2P connector terminal No. 1 and body ground.

Is there about 5 V?
YES - Go to step 12.

NO - Go to step 16.






12. Turn the ignition switch to LOCK (0).

13. Jump the SCS line with the HDS.

14. Disconnect ECM connector B (44P).

15. Check for continuity between ECT sensor 1 2P connector terminal No. 2 and ECM connector terminal B33.

Is there continuity?
YES - Go to step 27.

NO - Repair open in the wire between the ECM (B33) and ECT sensor 1, then go to step 22.






16. Turn the ignition switch to LOCK (0).

17. Jump the SCS line with the HDS.

18. Disconnect ECM connector B (44P).

19. Check for continuity between ECT sensor 1 2P connector terminal No. 1 and ECM connector terminal B23.

Is there continuity?
YES - Go to step 27.

NO - Repair open in the wire between the ECM (B23) and ECT sensor 1, then go to step 22.






20. Turn the ignition switch to LOCK (0).

21. Replace ECT sensor 1. ECT Sensor 1 Replacement

22. Reconnect all connectors.

23. Turn the ignition switch to ON (II).

24. Reset the ECM with the HDS.

25. Do the ECM idle learn procedure. ECM Idle Learn Procedure

26. Check for Temporary DTCs or DTCs with the HDS.

Is DTC P0118 indicated?
YES - Check for poor connections or loose terminals at ECT sensor 1 and the ECM, then go to step 1.

NO - Troubleshooting is complete. If any other Temporary DTCs or DTCs are indicated, go to the indicated DTC's troubleshooting.


27. Reconnect all connectors.

28. Update the ECM if it does not have the latest software, ECM Update or substitute a known-good ECM. Initial Inspection and Diagnostic Overview

29. Check for Temporary DTCs or DTCs with the HDS.

Is DTC P0118 indicated?
YES - Check for poor connections or loose terminals at ECT sensor 1 and the ECM. If the ECM was updated, substitute a known-good ECM, Initial Inspection and Diagnostic Overview then recheck. If the ECM was substituted, go to step 1.

NO - If the ECM was updated, troubleshooting is complete. If the ECM was substituted, replace the original ECM. Service and Repair If any other Temporary DTCs or DTCs are indicated, go to the indicated DTC's troubleshooting.