KX Models

Control System DTCs

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 How To Troubleshoot The Fuel And Emissions Systems.

1. ECT sensor 1 check:

ECT sensor 1 check
-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 (-12 °C) or less indicated?
-YES- Check for poor connections or loose terminals at ECT sensor 1, ECT sensor 2, and the ECM/PCM. If they are OK, replace ECT sensor 1 ECT Sensor 1 Removal and Installation, then do the repair verification.
-NO- Go to step 2.

2. Problem verification:

Problem verification
-1. Turn the ignition switch to LOCK (0).

-2. Allow the engine to cool to 104 °F (40 °C) or less.

-3. Start the engine, and let it idle until ECT SENSOR 1 goes up to about 158 °F (70 °C).

-4. Check ECT SENSOR 2 in the DATA LIST with the HDS.

Does ECT SENSOR 2 also read about 158 °F (70 °C)?
-YES- The failure is duplicated. 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, ECT sensor 2, and the ECM/PCM.

3. Thermostat check:

Thermostat check
-1. Check the thermostat Thermostat Removal, Installation, and Test.

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 terminals are OK, replace ECT sensor 1 ECT Sensor 1 Removal and Installation, then do the repair verification.
-NO- Replace the thermostat Thermostat Removal, Installation, and Test, then do the repair verification.

Repair verification:

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

-2. Reset the ECM/PCM with the HDS How To Troubleshoot The Fuel And Emissions Systems.

-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).

-6. Check ECT SENSOR 2 in the DATA LIST with the HDS.

Does ECT SENSOR 2 also read about 158 °F (70 °C)?
-YES- Check for poor connections or loose terminals at ECT sensor 1, ECT sensor 2, and the ECM/PCM, go to step 1.
-NO- Troubleshooting is complete. If the ECM/PCM was substituted, replace the original ECM/PCM Service and Repair. If any other Pending or Confirmed DTCs are indicated, go to the indicated DTC's troubleshooting.