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.

DTC Description
Confirmed DTC
Pending DTC
Freeze Frame
P0125 ECT Sensor 1 Malfunction/Slow Response
     

1.
ECT sensor 1 check:

ECT sensor 1 check
?1.
Start the engine, and let it idle for 5 minutes or more.

?2.
Check the parameter(s) below with the HDS.
Signal
Threshold
Current conditions
Values
Unit
Values
Unit
ECT SENSOR 1
Less than 10
°F
    

Do the current condition(s) match the threshold?

     
YES
     
     
     
Check for poor connections or loose terminals at ECT sensor 1, ECT sensor 2, and the PCM. If they are OK, replace ECT sensor 1, then do the repair verification.
     
NO
     
     
     
Go to step 2.
2.
Problem verification:

Problem verification
?1.
Press the engine start/stop button to select the OFF mode.

?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).
Signal
Current conditions
Values
Unit
ECT SENSOR 1
    

?4.
Check the parameter(s) below with the HDS.
Signal
Threshold
Current conditions
Values
Unit
Values
Unit
ECT SENSOR 2
About 158
°F
    

Do the current condition(s) match the threshold?

     
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 PCM.?
3.
Thermostat check:

Thermostat check
?1.
Check the thermostat.

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 terminals are OK, replace ECT sensor 1, then do the repair verification.
     
NO
     
     
     
Repair verification:

?1.
Press the engine start/stop button to select the ON mode.

?2.
Reset the PCM with the HDS.


?3.
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.
Start the engine, and let it idle until ECT SENSOR 1 goes up to about 158 °F (70 °C).
Signal
Current conditions
Values
Unit
ECT SENSOR 1
    

?6.
Check the parameter(s) below with the HDS.
Signal
Threshold
Current conditions
Values
Unit
Values
Unit
ECT SENSOR 2
About 158
°F
    


Do the current condition(s) match the threshold?

     
YES
     
     
     
Check for poor connections or loose terminals at ECT sensor 1, ECT sensor 2, and the PCM, go to step 1.
     
NO
     
     
     
Troubleshooting is complete. If the PCM was substituted, replace the original PCM. If any other Pending or Confirmed DTCs are indicated, go to the indicated DTC's troubleshooting.?