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. Reading and Clearing Diagnostic Trouble Codes

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 0 °F (-18 °C) or less indicated?
YES - Check for poor connections or loose terminals at ECT sensor 1, ECT sensor 2, and the ECM/PCM. If the connections and the terminals are OK, replace ECT sensor 1, ECT Sensor 1 Replacement then go to step 8.

NO - Go to step 3.


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

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

5. Start the engine, and let it idle until ECT SENSOR 1 goes up to about 158 °F (70 °C).

Does ECT SENSOR 2 also read about 158 °F (70 °C)?
YES - Go to step 6.

NO - 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 ECM/PCM.


6. Check the thermostat. Testing and Inspection

Is the thermostat OK?
YES - Check for poor connections or loose terminals at ECT sensor 1, ECT sensor 2, and the ECM/PCM. If the connections and the terminals are OK, replace ECT sensor 1, ECT Sensor 1 Replacement then go to step 7.

NO - Replace the thermostat, Thermostat Replacement then go to step 7.


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

8. Reset the ECM/PCM with the HDS.

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

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

11. Start the engine, and let it idle until ECT SENSOR 1 goes up to about 158 °F (70 °C).

Does ECT SENSOR 2 also read about 158 °F (70 °C)?
YES - Go to step 1 and recheck.

NO - Troubleshooting is complete.