Nissan Titan. Manual - part 224

P0125 ECT SENSOR

EC-197

< DTC/CIRCUIT DIAGNOSIS >

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P0125 ECT SENSOR

Component Description

INFOID:0000000009886600

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>

*: This data is reference value and is measured between ECM terminal 73 (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 ECM terminals, such as the ground.

On Board Diagnosis Logic

INFOID:0000000009886601

DTC Confirmation Procedure

INFOID:0000000009886602

CAUTION:

Be careful not to overheat engine.

NOTE:

• If DTC P0125 is displayed with P0117 or P0118, first perform the trouble diagnosis for DTC P0117,

P0118. Refer to 

EC-190, "DTC Confirmation Procedure"

.

• If DTC P0125 is displayed with P0116, first perform the trouble diagnosis for DTC P0116. Refer to 

EC-

186, "DTC Logic"

.

1. If DTC Confirmation Procedure has been previously conducted, always perform the following before con-

ducting the next step.

a. Turn ignition switch OFF and wait at least 10 seconds.
b. Turn ignition switch ON.
c. Turn ignition switch OFF and wait at least 10 seconds.
2. Turn ignition switch ON.
3. Select “DATA MONITOR” mode with CONSULT.

SEF594K

Engine coolant 

temperature

°C (°F)]

Voltage* (V)

Resistance (k

Ω)

–10 (14)

4.4

7.0 - 11.4

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
0125

Insufficient engine coolant 
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)

• Engine coolant temperature sensor
• Thermostat

EC-198

< DTC/CIRCUIT DIAGNOSIS >

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P0125 ECT SENSOR

4. Check that “COOLAN TEMP/S” is above 31

°C (88°F).

5. If it is above 31

°C (88°F), the test result will be OK.

6. If it is below 31

°C (88°F), go to following step.

7. Start engine and run it for 65 minutes at idle speed.

If “COOLAN TEMP/S” increases to more than 31

°C (88°F) within 65 minutes, stop engine because

the test result will be OK.

8. Check 1st trip DTC.
9. If 1st trip DTC is detected, go to 

EC-198, "Diagnosis Procedure"

.

Diagnosis Procedure

INFOID:0000000009886603

1.

CHECK GROUND CONNECTIONS

1. Turn ignition switch OFF.

2. Loosen and retighten three ground screws on the body.

Refer to 

EC-154, "Ground Inspection"

.

OK or NG

OK

>> GO TO 2.

NG

>> Repair or replace ground connections.

2.

CHECK ENGINE COOLANT TEMPERATURE SENSOR

Refer to 

EC-198, "Component Inspection"

.

OK or NG

OK

>> GO TO 3.

NG

>> Replace engine coolant temperature sensor. 

3.

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 4.

NG

>> Repair or replace thermostat. Refer to 

CO-22, "Removal and Installation"

.

4.

CHECK INTERMITTENT INCIDENT

Refer to 

GI-39, "How to Check Terminal"

 and 

GI-42, "Intermittent Incident"

.

For Wiring Diagram, refer to 

EC-88, "Wiring Diagram"

.

>> INSPECTION END

Component Inspection

INFOID:0000000009886604

ENGINE COOLANT TEMPERATURE SENSOR

BBIA0354E

P0125 ECT SENSOR

EC-199

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1. Check resistance between engine coolant temperature sensor

terminals 1 and 2 as shown in the figure.

2. If NG, replace engine coolant temperature sensor.

PBIB2005E

Engine coolant 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-200

< DTC/CIRCUIT DIAGNOSIS >

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P0127 IAT SENSOR

P0127 IAT SENSOR

Component Description

INFOID:0000000009886605

The intake air temperature sensor is built into mass air flow sensor.

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>

*: This data is reference value and is measured between ECM terminal 34 (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 ECM terminals, such as the ground.

On Board Diagnosis Logic

INFOID:0000000009886606

DTC Confirmation Procedure

INFOID:0000000009886607

NOTE:

If DTC Confirmation Procedure has been previously conducted, always perform the following before conduct-

ing the next step. 
1. Turn ignition swich OFF and wait at least 10 seconds.
2. Turn ignition swich ON.
3. Turn ignition swich OFF and wait at least 10 seconds.

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.
4. Wait until engine coolant temperature is less than 90

°C (194°F)

a. Turn ignition switch ON.
b. Select “DATA MONITOR” mode with CONSULT.
c.

Check the engine coolant temperature.

d. If the engine coolant temperature is not less than 90

°C (194°F), turn ignition switch OFF and cool down

engine.

BBIA0355E

Intake air temperature

°C (°F)]

Voltage* (V)

Resistance (k

Ω)

25 (77)

3.3

1.800- 2.200

80 (176)

1.2

0.283 - 0.359

SEF012P

DTC No.

Trouble diagnosis name

DTC detecting condition

Possible cause

P0127
0127

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