Nissan Frontier D22. Manual - part 566

DTC P0125 ECT SENSOR

EC-1367

[VG33ER]

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EC

DTC P0125 ECT SENSOR

PFP:22630

Component Description

UBS00DUH

NOTE:
If DTC P0125 is displayed with P0117 or P0118, first perform the trouble diagnosis for DTC P0117 or
P0118. Refer to 

EC-1345

 .

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 ther-
mistor decreases as temperature increases.

 <Reference data>

*: These data are reference values and are measured between ECM terminal 59
(Engine coolant temperature sensor) and ground.

CAUTION:

Do not use ECM ground terminals when measuring input/output voltage. Doing so may result in dam-
age to the ECM's transistor. Use a ground other than the ECM terminals, such as the ground.

On Board Diagnosis Logic

UBS00DUI

DTC Confirmation Procedure

UBS00DUJ

CAUTION:

Be careful not to overheat engine.

NOTE:
If DTC Confirmation Procedure has been previously conducted, always turn ignition switch OFF and wait at
least 5 seconds before conducting the next test.

 WITH CONSULT-II

1.

Turn ignition switch ON.

SEF594K

Engine coolant 

temperature

°C (°F)

Voltage*

(V)

Resistance

(k

Ω)

−10 (14)

4.4

9.2

20 (68)

3.5

2.1 - 2.9

50 (122)

2.2

0.68 - 1.00

90 (194)

0.9

0.236 - 0.260

SEF012P

DTC No.

Trouble diagnosis name

DTC detecting condition

Possible cause

P0125

Insufficient engine cool-
ant temperature for 
closed loop fuel control

●

Voltage sent to ECM from the sensor is not 
practical, even when some time has passed 
after starting the engine.

●

Engine coolant temperature is insufficient for 
closed loop fuel control.

●

Harness or connectors
(High resistance in the circuit)

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Engine coolant temperature sensor

●

Thermostat

EC-1368

[VG33ER]

DTC P0125 ECT SENSOR

2.

Select “DATA MONITOR” mode with CONSULT-II.

3.

Check that “COOLAN TEMP/S” is above 10

°C (50°F).

If it is above 10

°C (50°F), the test result will be OK.

If it is below 10

°C (50°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 10

°C (50°F)

within 65 minutes, stop engine because the test result will
be OK.

5.

If 1st trip DTC is detected, go to 

EC-1368, "Diagnostic Proce-

dure"

 .

 WITH GST

Follow the procedure “WITH CONSULT-II”.

Diagnostic Procedure

UBS00DUK

1. 

CHECK ENGINE COOLANT TEMPERATURE SENSOR

Refer to 

EC-1368, "Component Inspection"

 .

OK or NG

OK

>> GO TO 2.

 NG

>> Replace engine coolant temperature sensor.

2. 

CHECK THERMOSTAT OPERATION

When the engine is cold [lower than 70

°C (158°F)] condition, grasp lower radiator hose and confirm the engine

coolant does not flow.

OK or NG

OK

>> GO TO 3.

NG

>> Replace thermostat. Refer to 

CO-28, "THERMOSTAT"

 .

3. 

CHECK INTERMITTENT INCIDENT

Refer to 

EC-1297, "TROUBLE DIAGNOSIS FOR INTERMITTENT INCIDENT"

 .

>> INSPECTION END.

Component Inspection

UBS00DUL

ENGINE COOLANT TEMPERATURE SENSOR

1.

Check resistance as shown in the figure.

<Reference data>

SEF174Y

SEF152P

DTC P0125 ECT SENSOR

EC-1369

[VG33ER]

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2.

If NG, replace engine coolant temperature sensor.

Removal and Installation

UBS00DUM

ENGINE COOLANT TEMPERATURE SENSOR

Refer to 

EM-80, "OUTER COMPONENT PARTS"

 .

Temperature 

°C (°F)

Resistance k

Ω

20 (68)

2.1 - 2.9

50 (122) 

0.68 - 1.00

90 (194)

0.236 - 0.260

SEF012P

EC-1370

[VG33ER]

DTC P0127 IAT SENSOR

DTC P0127 IAT SENSOR

PFP:22630

Component Description

UBS00DUN

The intake air temperature sensor is mounted to the air duct hous-
ing. The sensor detects intake air temperature and transmits a signal
to the ECM.
The temperature sensing unit uses a thermistor which is sensitive to
the change in temperature. Electrical resistance of the thermistor
decreases in response to the temperature rise.

<Reference data>

*: These data are reference values and are measured between ECM terminal 61
(Intake air temperature sensor) and ground.

CAUTION:

Do not 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 the ECM terminals, such as the ground.

On Board Diagnosis Logic

UBS00DUO

DTC Confirmation Procedure

UBS00DUP

NOTE:
If DTC Confirmation Procedure has been previously conducted, always turn ignition switch OFF and wait at
least 5 seconds before conducting the next test.

CAUTION:

Always drive vehicle at a safe speed.
TESTING CONDITION:
This test may be conducted with the drive wheels lifted in the shop or by driving the vehicle. If a road
test is expected to be easier, it is unnecessary to lift the vehicle.

 WITH CONSULT-II

1.

Wait until engine coolant temperature is less than 90

°C (194°F).

a.

Turn ignition switch ON.

LEC519

Intake air 

temperature

°C (°F)

Voltage*

(V)

Resistance

k

Ω

20 (68)

3.5

2.1 - 2.9

80 (176)

1.23

0.27 - 0.38

SEF012P

DTC No.

Trouble diagnosis name

DTC detecting condition

Possible cause

P0127

Intake air temperature 
too high

Rationally incorrect voltage from the sensor is 
sent to ECM, compared with the voltage signal 
from engine coolant temperature sensor.

●

Harness or connectors
(The sensor circuit is open or shorted)

●

Intake air temperature sensor