Nissan Titan. Manual - part 225

P0127 IAT SENSOR

EC-201

< DTC/CIRCUIT DIAGNOSIS >

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

°C (194°F).

5. Turn ignition switch ON.
6. Select “DATA MONITOR” mode with CONSULT.
7. Start engine.
8. Hold vehicle speed at more than 70 km/h (43 MPH) for 100 consecutive seconds.
9. Check 1st trip DTC.
10. If 1st trip DTC is detected, go to 

EC-201, "Diagnosis Procedure"

.

Diagnosis Procedure

INFOID:0000000009886608

1.

CHECK GROUND CONNECTIONS

1. Turn ignition switch OFF.

2. Loosen and retighten three ground screws on the body. 

Refer to 

EC-154, "Ground Inspection"

.

OK or NG

OK

>> GO TO 2.

NG

>> Repair or replace ground connections.

2.

CHECK INTAKE AIR TEMPERATURE SENSOR

Refer to 

EC-201, "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 

GI-39, "How to Check Terminal"

 and 

GI-42, "Intermittent Incident"

.

For wiring diagram, refer to 

EC-88, "Wiring Diagram"

.

>> INSPECTION END

Component Inspection

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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).

BBIA0354E

Intake air temperature 

°C (°F)]

Resistance (k

Ω)

25 (77)

1.800 - 2.200

BBIA0355E

EC-202

< DTC/CIRCUIT DIAGNOSIS >

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P0127 IAT SENSOR

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P0128 THERMOSTAT FUNCTION

EC-203

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P0128 THERMOSTAT FUNCTION

On Board Diagnosis Logic

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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-262, "DTC Confirmation Procedure"

.

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

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NOTE:

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

ing the next step. 
1. Turn ignition swich OFF and wait at least 10 seconds.
2. Turn ignition swich ON.
3. Turn ignition swich 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 52°C (126°F).

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

6. If it is below 52

°C (126°F), go to following step.

7. If it is above 52

°C (126°F), cool down the engine to less than 52°C (126°F). Then go to next steps.

8. Start engine and wait at idle for at 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.

9. Check 1st trip DTC.

10. If 1st trip DTC is detected, go to 

EC-203, "Diagnosis Procedure"

.

Diagnosis Procedure

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1.

CHECK ENGINE COOLANT TEMPERATURE SENSOR

Refer to 

EC-204, "Component Inspection"

.

OK or NG

OK

>> GO TO 2.

NG

>> Replace engine coolant temperature sensor.

2.

CHECK THERMOSTAT

Refer to 

CO-22, "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 engine has run long enough.

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

EC-204

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P0128 THERMOSTAT FUNCTION

Component Inspection

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ENGINE COOLANT TEMPERATURE SENSOR

1. Check resistance between engine coolant temperature sensor

terminals 1 and 2 as shown in the figure.

2. If NG, replace engine coolant temperature sensor.

PBIB2005E

Engine coolant temperature

°C (°F)]

Resistance (k

Ω)

20 (68)

2.1 - 2.9

50 (122)

0.68 - 1.00

90 (194)

0.236 - 0.260

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