Infiniti F50. Manual - part 391

DTC P0127 IAT SENSOR

EC-205

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EC

DTC P0127 IAT SENSOR

PFP:22630

Component Description

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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 99
(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 termi-
nals, such as the ground.

On Board Diagnosis Logic

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SEC266C

Intake air 

temperature

°

C (

°

F)

Voltage*

V

Resistance

k

Ω

−

10 (14)

4.43

7.9 - 9.3

25 (77)

3.32

1.9 - 2.1

80 (176)

1.23

0.31 - 0.37

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-206

DTC P0127 IAT SENSOR

DTC Confirmation Procedure

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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-II

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-II.

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 tempera-
ture reaches 90

°

C (194

°

F).

2.

Turn ignition switch “ON”.

3.

Select “DATA MONITOR” mode with CONSULT-II.

4.

Start engine.

5.

Hold vehicle speed at more than 71 km/h (44 MPH) for 100 con-
secutive seconds.

6.

If 1st trip DTC is detected, go to 

EC-208, "Diagnostic Procedure"

 .

 WITH GST

Follow the procedure “WITH CONSULT-II” above.

PBIB1917E

DTC P0127 IAT SENSOR

EC-207

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Wiring Diagram

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TBWM0008E

EC-208

DTC P0127 IAT SENSOR

Diagnostic Procedure

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1. 

CHECK INTAKE AIR TEMPERATURE SENSOR POWER SUPPLY CIRCUIT

1.

Turn ignition switch “OFF”.

2.

Disconnect mass air flow sensor (intake air temperature sensor
is built-into) harness connector.

3.

Turn ignition switch “ON”.

4.

Check voltage between mass air flow sensor terminal 5 and
ground.

OK or NG

OK

>> GO TO 2.

NG

>> Repair harness or connectors.

2. 

CHECK INTAKE AIR TEMPERATURE SENSOR GROUND CIRCUIT FOR OPEN AND SHORT

1.

Turn ignition switch “OFF”.

2.

Disconnect ECM.

3.

Check harness continuity between mass air flow sensor terminal 3 and ECM terminal 109.
Refer to Wiring Diagram.

4.

Also check harness for short to ground and short to power.

OK or NG

OK

>> GO TO 3.

NG

>> Repair open circuit or short to ground or short to power in harness or connectors.

3. 

CHECK INTAKE AIR TEMPERATURE SENSOR

Refer to 

EC-209, "Component Inspection"

 .

OK or NG

OK

>> GO TO 4.

NG

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

4. 

CHECK INTERMITTENT INCIDENT

Refer to 

EC-132, "TROUBLE DIAGNOSIS FOR INTERMITTENT INCIDENT"

 .

>> INSPECTION END

PBIB0012E

Voltage: Approximately 5 V

PBIB0066E

Continuity should exist.