P0125

P0125 ECT Sensor

Component Description

The engine coolant temperature sensor is used to detect the engine coolant temperature. The sensor modifies a voltage signal from the ECM. The modified signal returns to the ECM as the engine coolant temperature input. The sensor uses a thermistor which is sensitive to the change in temperature. The electrical resistance of the thermistor decreases as temperature increases.





[Reference data]









*: This data is reference value and is measured between ECM terminal 73 (Engine coolant temperature sensor) and ground.

CAUTION:

Never use ECM ground terminals when measuring input/output voltage. Doing so may result in damage to the ECM's transistor. Use a ground other than ECM terminals, such as the ground.

On Board Diagnosis Logic

NOTE:

If DTC P0125 is displayed with P0116, first perform the trouble diagnosis for DTC P0116. Refer to [P0116 ECT Sensor] P0116.

NOTE:

If DTC P0125 is displayed with P0117 or P0118, first perform the trouble diagnosis for DTC P0117 or P0118. Refer to [P0117, P0118 ECT Sensor] P0117.






DTC Confirmation Procedure

CAUTION:

Never overheat engine.

NOTE:

If DTC Confirmation Procedure has been previously conducted, always perform the following before conducting the next step.

1) Turn ignition switch OFF and wait at least 10 seconds.
2) Turn ignition switch ON.
3) Turn ignition switch OFF and wait at least 10 seconds.

with SDT

1 Turn ignition switch ON.
2 Select "Data list" mode with SDT.
3 Check that "COOLAN TEMP/S" is above 20 °C (68 °F).
If the temperature is above 20 °C (68 °F), the test result will be OK.
If the temperature is below 20 °C (68 °F), go to following step.
4 Start engine and run it for 65 minutes at idle speed.
If "COOLAN TEMP/S" increases to more than 20 °C (68 °F) within 65 minutes, stop engine because the test result will be OK.
5 Check 1st trip DTC.
6 If 1st trip DTC is detected, go to "Diagnosis Procedure".

with GST

Follow the procedure "WITH SDT" above.

Diagnosis Procedure

1. CHECK GROUND CONNECTIONS

1 Turn ignition switch OFF.
2 Loosen and retighten three ground screws on the body. Refer to [Power Supply and Ground Circuit Check] Power Supply and Ground Circuit Check.






OK or NG
OK
GO TO 2.
NG
Repair or replace ground connections.

2. CHECK ENGINE COOLANT TEMPERATURE SENSOR

Refer to "Component Inspection".

OK or NG
OK
GO TO 3.
NG
Replace engine coolant temperature sensor. Refer to [Water Outlet and Water Piping: Exploded View] Water Outlet Exploded View.

3. CHECK THERMOSTAT OPERATION

When the engine is cold [lower than 70 °C (158 °F)] condition, grasp lower radiator hose and confirm that the engine coolant does not flow.

OK or NG
OK
GO TO 4.
NG
Repair or replace thermostat. Refer to [Water Inlet and Thermostat Assembly: Removal and Installation] Water Inlet and Thermostat Assembly Removal and Installation.

4. CHECK INTERMITTENT INCIDENT

Refer to [Service Information for Electrical Incident: Intermittent Incident] Service Information for Electrical Incident: Intermittent Incident.


INSPECTION END

Component Inspection

Engine Coolant Temperature Sensor

1) Check resistance between engine coolant temperature sensor terminals 1 and 2 as shown in the figure.





[Reference data]











2) If NG, replace engine coolant temperature sensor.