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 indicated?
YES - Check for poor connections or loose terminals at ECT sensor 1, ECT sensor 2, and the 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), or press the engine start/stop button to select the OFF mode.

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

5. Make sure the temperature difference between ECT SENSOR 1 and ECT SENSOR 2 is about 50 °F (10 °C) in the DATA LIST with the HDS.

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

Does ECT sensor 2 also show about 158 °F (70 °C)?
YES - Go to step 7.

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 PCM.


7. 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 PCM. If the connections and the terminals are OK, replace ECT sensor 1, ECT Sensor 1 Replacement then go to step 8.

NO - Replace the thermostat, Service and Repair then go to step 8.


8. Turn the ignition switch to ON (II), or press the engine start/stop button to select the ON mode.

9. Reset the PCM with the HDS.

10. Turn the ignition switch to LOCK (0), or press the engine start/stop button to select the OFF mode.

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

12. Make sure the temperature difference between ECT SENSOR 1 and ECT SENSOR 2 is about 50 °F (10 °C) in the DATA LIST with the HDS.

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

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

NO - Troubleshooting is complete.