Infiniti FX35, FX50 (S51). Manual - part 815

 

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Infiniti FX35, FX50 (S51). Manual - part 815

 

 

P0127 IAT SENSOR

EC-801

< DTC/CIRCUIT DIAGNOSIS >

[VK50VE]

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P0127 IAT SENSOR

Description

INFOID:0000000005237284

The intake air temperature sensor is built-into the mass air flow sen-
sor (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 rise in temperature.

<Reference data>

*: These data are reference values and are measured between ECM terminals 48
(Intake air temperature sensor) and 42 (Sensor ground).

DTC Logic

INFOID:0000000005237285

DTC DETECTION LOGIC

DTC CONFIRMATION PROCEDURE

1.

PRECONDITIONING

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.

2.

Turn ignition switch ON.

3.

Turn ignition switch OFF and wait at least 10 seconds.

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.

>> GO TO 2.

2.

PERFORM DTC CONFIRMATION PROCEDURE

 With CONSULT-III

1.

Wait until engine coolant temperature is less than 90

°

C (194

°

F)

-

Turn ignition switch ON.

-

Select “DATA MONITOR” mode with CONSULT-III.

-

Check the engine coolant temperature.

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

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-802

< DTC/CIRCUIT DIAGNOSIS >

[VK50VE]

P0127 IAT SENSOR

-

If the engine coolant temperature is not less than 90

°

C (194

°

F), turn ignition switch OFF and cool down

engine.

NOTE:
Perform the following steps before engine coolant temperature is above 90

°

C (194

°

F).

2.

Turn ignition switch ON.

3.

Select “DATA MONITOR” mode with CONSULT-III.

4.

Start engine.

5.

Hold vehicle speed at more than 70 km/h (43 MPH) for 100 consecutive seconds.

CAUTION:

Always drive vehicle at a safe speed.

6.

Check 1st trip DTC.

 With GST

Follow the procedure “With CONSULT-III” above.
Is 1st trip DTC detected?

YES

>> Go to 

EC-802, "Diagnosis Procedure"

.

NO

>> INSPECTION END

Diagnosis Procedure

INFOID:0000000005237286

1.

CHECK GROUND CONNECTION

1.

Turn ignition switch OFF.

2.

Check ground connection M95. Refer to Ground Inspection in 

GI-39, "Circuit Inspection"

.

Is the inspection result normal?

YES

>> GO TO 2.

NO

>> Repair or replace ground connection.

2.

CHECK INTAKE AIR TEMPERATURE SENSOR

Refer to 

EC-802, "Component Inspection"

.

Is the inspection result normal?

YES

>> GO TO 3.

NO

>> Replace mass air flow sensor (bank 1) (with intake air temperature sensor).

3.

CHECK INTERMITTENT INCIDENT

Refer to 

GI-36, "Intermittent Incident"

.

>> INSPECTION END

Component Inspection

INFOID:0000000005237287

1.

CHECK INTAKE AIR TEMPERATURE SENSOR

1.

Turn ignition switch OFF.

2.

Disconnect mass air flow sensor (bank 1) harness connector.

3.

Check resistance between mass air flow sensor (bank 1) terminals as per the following.

Is the inspection result normal?

YES

>> INSPECTION END

NO

>> Replace mass air flow sensor (bank 1) (with intake air temperature sensor).

Terminals

Condition

Resistance (k

Ω

)

1 and 2

Temperature [

°

C (

°

F)]

25 (77)

1.800 - 2.200

P0128 THERMOSTAT FUNCTION

EC-803

< DTC/CIRCUIT DIAGNOSIS >

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P0128 THERMOSTAT FUNCTION

DTC Logic

INFOID:0000000005237288

DTC DETECTION LOGIC

NOTE:
If DTC P0128 is displayed with DTC P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307 or P0308,
first perform the trouble diagnosis for DTC P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307,
P0308. Refer to 

EC-864, "DTC Logic"

.

Engine coolant temperature has not risen enough to open the thermostat even though the engine has run long
enough.
This is due to a leakage in the seal or the thermostat being stuck open.

DTC CONFIRMATION PROCEDURE

1.

PRECONDITIONING

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.

2.

Turn ignition switch ON.

3.

Turn ignition switch OFF and wait at least 10 seconds.

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.

>> GO TO 2.

2.

PERFORM DTC CONFIRMATION PROCEDURE

 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 56

°

C (133

°

F), go to next step.

If it is above 56

°

C (133

°

F), cool engine down to less than 56

°

C (133

°

F). Then go to next step.

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.

 With GST

Follow the procedure “With CONSULT-III” above.

Is 1st trip DTC detected?

YES

>> Go to 

EC-804, "Diagnosis Procedure"

.

NO

>> INSPECTION END

DTC No.

Trouble diagnosis name

DTC detecting condition

Possible cause

P0128

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

Vehicle speed

More than 56 km/h (35 MPH)

EC-804

< DTC/CIRCUIT DIAGNOSIS >

[VK50VE]

P0128 THERMOSTAT FUNCTION

Diagnosis Procedure

INFOID:0000000005237289

1.

CHECK ENGINE COOLANT TEMPERATURE SENSOR

Refer to 

EC-804, "Component Inspection"

.

Is the inspection result normal?

YES

>> INSPECTION END

NO

>> GO TO 2.

2.

CHECK THERMOSTAT

Refer to 

CO-46, "Removal and Installation"

.

Is the inspection result normal?

YES

>> INSPECTION END

NO

>> Replace thermostat.

Component Inspection

INFOID:0000000005237290

1.

CHECK ENGINE COOLANT TEMPERATURE SENSOR

1.

Turn ignition switch OFF.

2.

Disconnect engine coolant temperature sensor harness connector.

3.

Remove engine coolant temperature sensor.

4.

Check resistance between engine coolant temperature sensor
terminals by heating with hot water as shown in the figure.

Is the inspection result normal?

YES

>> INSPECTION END

NO

>> Replace engine coolant temperature sensor.

Terminals

Condition

Resistance (k

Ω

)

1 and 2

Temperature [

°

C (

°

F)]

20 (68)

2.37 - 2.63

50 (122)

0.68 - 1.00

90 (194)

0.236 - 0.260

JMBIA0080ZZ

 

 

 

 

 

 

 

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