DTC Troubleshooting

DTC Troubleshooting: P0125

DTC P0125: ECT Sensor 1 Malfunction/Slow Response

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. Start the engine, and let it idle for 5 minutes or more.

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

Is about 10 °F (-12 °C) or less, or 4.45 V or more indicated?
YES - Go to step 9.

NO - Go to step 3.


3. Allow the engine to cool to 104 °F (40 °C) or less.

4. Note the value of ECT SENSOR 1 and ECT SENSOR 2 in the DATA LIST with the HDS.

5. Start the engine, and let it idle.

6. Let the engine idle until ECT SENSOR 1 goes up 49 °F (27 °C) or more from the recorded temperature.

7. Note the value of ECT SENSOR 2 in the DATA LIST with the HDS.

8. Compare ECT SENSOR 2 and the recorded temperature.

Did ECT SENSOR 2 change 17 °F (9.5 °C) or more?
YES - Intermittent failure, the system is OK at this time. Check for poor connections or loose terminals at ECT sensor 1, ECT sensor 2, and the PCM.

NO - Check the thermostat. Testing and Inspection If the thermostat is OK, go to step 9. If the thermostat is faulty, replace it, Service and Repair then go to step 11.


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

10. Replace ECT sensor 1. ECT Sensor 1 Replacement

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

12. Reset the PCM with the HDS.

13. Do the PCM idle learn procedure. PCM Idle Learn Procedure

14. Allow the engine to cool to ambient temperature.

15. Start the engine, and let it idle for 20 minutes.

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

Is DTC P0125 indicated?
YES - Check for poor connections or loose terminals at the ECT sensor 2 and the PCM, then go to step 1.

NO - Go to step 17.


17. Monitor the OBD STATUS for DTC P0125 in the DTCs MENU with the HDS.

Does the screen indicate PASSED?
YES - Troubleshooting is complete. If any other Temporary DTCs or DTCs were indicated in step 16, go to the indicated DTC's troubleshooting.

NO - If the screen indicates FAILED, check for poor connections or loose terminals at the ECT sensor 2 and the PCM, then go to step 1. If the screen indicates NOT COMPLETED, go to step 14.