DTC Troubleshooting: P0125
DTC P0125: ECT Sensor 1 Malfunction/Slow Response
NOTE: Before you troubleshoot, review the general troubleshooting information.

DTC Description
Confirmed DTC
Pending DTC
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 0
°F
    
Less than -18
°C

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.?
     
NO
     
     
     
Go to step 2.
2.
Problem verification:

Problem verification
?1.
Turn the vehicle to the OFF (LOCK) 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
    
About 70
°C

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. If the on-board snapshot of this DTC is recorded, try to reproduce the failure under the same conditions with the on-board snapshot.?
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.?
     
NO