Infiniti FX35 / FX45. Manual - part 508

 

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Infiniti FX35 / FX45. Manual - part 508

 

 

DTC P0127 IAT SENSOR

EC-793

< SERVICE INFORMATION >

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DTC P0127 IAT SENSOR

Component Description

INFOID:0000000001326631

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>

*: These data are reference values and are 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:0000000001326632

DTC Confirmation Procedure

INFOID:0000000001326633

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.

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-III

1.

Wait until engine coolant temperature is less than 90

°

C (194

°

F)

a.

Turn ignition switch ON.

b.

Select “DATA MONITOR” mode with CONSULT-III.

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.
• Perform the following steps before engine coolant temperature is above 90

°

C (194

°

F).

2.

Start engine.

PBIB1604E

Intake air temperature

°

C (

°

F)

Voltage*

V

Resistance

k

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-794

< SERVICE INFORMATION >

[VK45DE]

DTC P0127 IAT SENSOR

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-794, "Diagnosis Procedure"

.

 WITH GST

Follow the procedure “WITH CONSULT-III” above.

Diagnosis Procedure

INFOID:0000000001326634

1.

CHECK GROUND CONNECTIONS

1.

Turn ignition switch OFF.

2.

Loosen and retighten three ground screws on the body.
Refer to 

EC-723, "Ground Inspection"

.

OK or NG

OK

>> GO TO 2.

NG

>> Repair or replace ground connections.

2.

CHECK INTAKE AIR TEMPERATURE SENSOR

Refer to 

EC-778, "Component Inspection"

.

OK or NG

OK

>> GO TO 3.

NG

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

3.

CHECK INTERMITTENT INCIDENT

Refer to 

EC-717

.

Refer to 

EC-776, "Wiring Diagram"

.

>> INSPECTION END

Component Inspection

INFOID:0000000001326635

INTAKE AIR TEMPERATURE SENSOR

1.

Check resistance between intake air temperature sensor termi-
nals 5 and 6 under the following conditions.

2.

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

PBIB2195E

Intake air temperature 

°

C (

°

F)

Resistance k

25 (77)

1.800 - 2.200

PBIB1604E

DTC P0127 IAT SENSOR

EC-795

< SERVICE INFORMATION >

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Removal and Installation

INFOID:0000000001326636

MASS AIR FLOW SENSOR

Refer to 

EM-173

.

SEF012P

EC-796

< SERVICE INFORMATION >

[VK45DE]

DTC P0128 THERMOSTAT FUNCTION

DTC P0128 THERMOSTAT FUNCTION

On Board Diagnosis Logic

INFOID:0000000001326637

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 stuck open.

DTC Confirmation Procedure

INFOID:0000000001326638

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 71

°

C (160

°

F).

• Before performing the following procedure, do not fill with the fuel.

 WITH CONSULT-III

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-III.

5.

Check the indication of “COOLAN TEMP/S”.
If it is below 71

°

C (160

°

F), go to following step.

If it is above 71

°

C (160

°

F), cool down the engine to less than 71

°

C (160

°

F), then go to next step.

6.

Start engine.

7.

Wait at idle for a least 30 minutes.
If “COOLAN TEMP/S” increases to more than 71

°

C (160

°

F) within 30 minutes, turn ignition switch

OFF because the test result will be OK.

8.

Check 1st trip DTC.

9.

If 1st trip DTC is detected, go to 

EC-796, "Diagnosis Procedure"

.

 WITH GST

Follow the procedure “WITH CONSULT-III” above.

Diagnosis Procedure

INFOID:0000000001326639

1.

CHECK ENGINE COOLANT TEMPERATURE SENSOR

Refer to 

EC-797, "Component Inspection"

.

OK or NG

OK

>> GO TO 2.

NG

>> Replace engine coolant temperature sensor.

2.

CHECK THERMOSTST

Refer to 

CO-53, "Removal and Installation"

.

OK or NG

OK

>> INSPECTION END

NG

>> Replace thermostat.

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 en-
gine has run long enough.

• Thermostat
• Leakage from sealing portion of thermo-

stat

• Engine coolant temperature sensor

 

 

 

 

 

 

 

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