Nissan Altima L32. Manual - part 525

P0127 IAT SENSOR

EC-1221

< COMPONENT DIAGNOSIS >

[VQ35DE]

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P0127 IAT SENSOR

Description

INFOID:0000000004362074

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 50
(Intake air temperature sensor) and 56 (Sensor ground).

DTC Logic

INFOID:0000000004362075

DTC DETECTION LOGIC

DTC CONFIRMATION PROCEDURE

1.

PRECONDITIONING

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

ing 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-1222

< COMPONENT DIAGNOSIS >

[VQ35DE]

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 approximately 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-1222, "Diagnosis Procedure"

.

NO

>> INSPECTION END

Diagnosis Procedure

INFOID:0000000004362076

1.

CHECK GROUND CONNECTION

1. Turn ignition switch OFF.

2. Check ground connection E9. Refer to Ground Inspection in 

GI-45, "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-1222, "Component Inspection"

.

Is the inspection result normal?

YES

>> GO TO 3.

NO

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

3.

CHECK INTERMITTENT INCIDENT

Refer to 

GI-42, "Intermittent Incident"

.

>> INSPECTION END

Component Inspection

INFOID:0000000004362077

1.

CHECK INTAKE AIR TEMPERATURE SENSOR

1. Turn ignition switch OFF.

2. Disconnect mass air flow sensor harness connector.

3. Check resistance between mass air flow sensor terminals as per

the following.

Is the inspection result normal?

YES

>> INSPECTION END

NO

>> Replace mass air flow sensor (with intake air tempera-

ture sensor).

Terminal

Condition

Resistance (k

Ω)

1 and 2

Temperature [

°C (°F)]

25 (77)

1.800 - 2.200

JMBIA1624ZZ

P0128 THERMOSTAT FUNCTION

EC-1223

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P0128 THERMOSTAT FUNCTION

DTC Logic

INFOID:0000000004362078

DTC DETECTION LOGIC

NOTE:

If DTC P0128 is displayed with DTC P0300, P0301, P0302, P0303, P0304, P0305 or P0306, first perform

the trouble diagnosis for DTC P0300, P0301, P0302, P0303, P0304, P0305, P0306. Refer to 

EC-1283,

"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 before conduct-

ing 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 down the engine to less than 56°C (133°F). Then go to next steps.

6. Start engine.

7. 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.

8. Check 1st trip DTC.

With GST

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

YES

>> Go to 

EC-1224, "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 en-
gine has run long enough.

• Thermostat
• Leakage from sealing portion of thermo-

stat

• Engine coolant temperature sensor

VHCL SPEED SE

More than 56 km/h (35 MPH)

EC-1224

< COMPONENT DIAGNOSIS >

[VQ35DE]

P0128 THERMOSTAT FUNCTION

Diagnosis Procedure

INFOID:0000000004362079

1.

CHECK ENGINE COOLANT TEMPERATURE SENSOR

Refer to 

EC-1224, "Component Inspection"

.

Is the inspection result normal?

YES

>> GO TO 2.

NO

>> Replace engine coolant temperature sensor.

2.

CHECK THERMOSTAT

Check thermostat. Refer to 

CO-46, "Removal and Installation"

.

Is the inspection result normal?

YES

>> INSPECTION END

NO

>> Replace thermostat.

Component Inspection

INFOID:0000000004362080

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 as per the following.

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)

2.1 - 2.9

50 (122)

0.68 - 1.00

90 (194)

0.236 - 0.260

PBIB2005E