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Nissan Frontier. Manual - part 405

P0127 IAT SENSOR

EC-191

< DTC/CIRCUIT DIAGNOSIS >

[QR25DE]

P0127 IAT SENSOR

Component Description

INFOID:0000000009480843

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

(1). 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 50 (Intake air
temperature sensor) and 56 (sensor 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

INFOID:0000000009480844

DTC Confirmation Procedure

INFOID:0000000009480845

CAUTION:

Always drive vehicle at a safe speed.

NOTE:

If DTC Confirmation Procedure has been previously conducted, always turn ignition switch OFF and wait at

least 10 seconds before conducting the next test.

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

1. Wait until engine coolant temperature is less than 96

°C (205°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 96

°C (205°F), turn ignition switch OFF and cool down

engine.

• Perform the following steps before engine coolant temperature is above 96

°C (205°F).

PBIA9559J

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

EC-192

< DTC/CIRCUIT DIAGNOSIS >

[QR25DE]

P0127 IAT SENSOR

2. Start engine.
3. Hold vehicle speed at more than 70 km/h (43 MPH) for 100 consecutive seconds.
4. Check 1st trip DTC.
5. If 1st trip DTC is detected, go to

EC-192, "Diagnosis Procedure"

WITH GST

Follow the procedure With CONSULT above.

Diagnosis Procedure

INFOID:0000000009480846

CHECK GROUND CONNECTIONS

1. Turn ignition switch OFF.

2. Loosen and retighten two ground screws on the body. Refer to

EC-149, "Ground Inspection"

OK or NG

>> GO TO 2.

>> Repair or replace ground connections.

CHECK INTAKE AIR TEMPERATURE SENSOR

Refer to

EC-192, "Component Inspection"

OK or NG

>> GO TO 3.

>> Replace mass air flow sensor (with intake air temperature sensor). Refer to

EM-25, "Exploded

View"

CHECK INTERMITTENT INCIDENT

Refer to

GI-42, "Intermittent Incident"

>> INSPECTION END

Component Inspection

INFOID:0000000009480847

INTAKE AIR TEMPERATURE SENSOR

1. Check resistance between mass air flow sensor (1) terminals 5

and 6 under the following conditions.

2. If NG, replace mass air flow sensor (with intake air temperature

sensor).

BBIA0614E

Intake air temperature

°C (°F)

Resistance k

Ω

25 (77)

1.800 - 2.200

PBIA9559J

P0127 IAT SENSOR

EC-193

< DTC/CIRCUIT DIAGNOSIS >

[QR25DE]

SEF012P

EC-194

< DTC/CIRCUIT DIAGNOSIS >

[QR25DE]

P0128 THERMOSTAT FUNCTION

P0128 THERMOSTAT FUNCTION

On Board Diagnosis Logic

INFOID:0000000009480848

NOTE:

If DTC P0128 is displayed with DTC P0300, P0301, P0302, P0303 or P0304, first perform the trouble

diagnosis for DTC P0300, P0301, P0302, P0303, P0304. Refer to

EC-249, "DTC Confirmation Proce-

dure"

Engine coolant temperature has not risen enough to open the thermostat even though the engine has run long

enough.

This is due to a leak in the seal or the thermostat being stuck open.

DTC Confirmation Procedure

INFOID:0000000009480849

FOR A/T MODELS

With CONSULT

NOTE:

If DTC Confirmation Procedure has been previously conducted, always turn ignition switch OFF and wait at

least 10 seconds before conducting the next test.

TESTING CONDITION:

• For best results, perform at ambient temperature of –10

°C (14°F) or higher.

• For best results, perform at engine coolant temperature of –10

°C (14°F) to 56°C (133°F).

• Before performing the following procedure, do not add fuel.
1. Turn A/C switch OFF.
2. Turn blower fan switch OFF.
3. Turn ignition switch ON.
4. Select “COOLAN TEMP/S” in “DATA MONITOR” mode with CONSULT.
5. Check the indication of “COOLAN TEMP/S”.

If it is below 56

°C (133°F), go to next step.

If it is above 56

°C (133°F), cool down the engine to less than 56°C (133°F). then go to next steps.

6. Start engine and drive vehicle for 10 consecutive minutes under the following conditions.

CAUTION:

Always drive vehicle at a safe speed.

NOTE:

If “COOLAN TEMP/S” increases to more than 75

°C (167°F) within 10 minutes, turn ignition switch

OFF because the test result will be OK.

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

EC-196, "Diagnosis Procedure"

With GST

Follow the procedure “With CONSULT” above.

FOR M/T MODELS

NOTE:

Never refuel before and during the following procedure.

PRECONDITIONING-1

If DTC Confirmation Procedure has been previously conducted, always perform the following procedure

before conducting the next test.

1. Turn ignition switch OFF and wait at least 10 seconds.

DTC No.

Trouble diagnosis name

DTC detecting condition

Possible cause

P0128
0128

Thermostat function

The engine coolant temperature does not
reach to specified temperature even though
the engine has run long enough.

• Thermostat
• Leakage from sealing portion of thermostat
• Engine coolant temperature sensor

VHCL SPEED SE

More than 56km/h (35 MPH)

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