Infiniti G37 Coupe. Manual — part 503
P0127 IAT SENSOR
EC-193
< COMPONENT DIAGNOSIS >
[VQ37VHR]
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P0127 IAT SENSOR
Description
INFOID:0000000001910830
The intake air temperature sensor is built-into mass air flow sensor
(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 temperature rise.
NOTE:
ECM uses only the intake air temperature sensor (bank 1) for engine
control and self-diagnosis. It does not use the intake air temperature
sensor (bank 2).
<Reference data>
*: These data are reference values and are measured between ECM terminal 67
(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.
DTC Logic
INFOID:0000000001734026
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.
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-194
< COMPONENT DIAGNOSIS >
[VQ37VHR]
P0127 IAT SENSOR
-
Check the engine coolant temperature.
-
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
NO
>> INSPECTION END
Diagnosis Procedure
INFOID:0000000001734027
1.
CHECK GROUND CONNECTION
1.
Turn ignition switch OFF.
2.
Check ground connection M95. Refer to Ground Inspection in
Is the inspection result normal?
YES
>> GO TO 2.
NO
>> Repair or replace ground connection.
2.
CHECK INTAKE AIR TEMPERATURE SENSOR
EC-194, "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
GI-38, "Intermittent Incident"
>> INSPECTION END
Component Inspection
INFOID:0000000001910831
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 follows.
Is the inspection result normal?
YES
>> INSPECTION END
NO
>> Replace mass air flow sensor (with intake air temperature sensor) (bank 1).
Terminals
Condition
Resistance
1 and 2
Temperature
°
C (
°
F)
25 (77)
1.800 - 2.200 k
Ω
P0128 THERMOSTAT FUNCTION
EC-195
< COMPONENT DIAGNOSIS >
[VQ37VHR]
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P0128 THERMOSTAT FUNCTION
DTC Logic
INFOID:0000000001734029
DTC DETECTION 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 leak in the seal or the thermostat 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 60
°
C (140
°
F).
>> GO TO 2.
2.
PERFORM DTC CONFIRMATION PROCEDURE
With CONSULT-III
1.
Replace thermostat with new one. Refer to
CO-22, "Removal and Installation"
. Use only a genuine NIS-
SAN thermostat as a replacement. If an incorrect thermostat is used, the MIL may come on.
2.
Turn ignition switch ON.
3.
Select “COOLAN TEMP/S” in “DATA MONITOR” mode with CONSULT-III.
4.
Check the indication of “COOLAN TEMP/S”.
If it is below 60
°
C (140
°
F), go to the following steps.
If it is above 60
°
C (140
°
F), cool engine down to less than 60
°
C (140
°
F). Then go to next step.
5.
Drive vehicle for 10 consecutive minutes under the following conditions.
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
NO
>> INSPECTION END
Diagnosis Procedure
INFOID:0000000001734030
1.
CHECK ENGINE COOLANT TEMPERATURE SENSOR
EC-196, "Component Inspection"
Is the inspection result normal?
YES
>> INSPECTION END
NO
>> Replace engine coolant temperature sensor.
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
80 - 120 km/h (50 - 75 mph)
EC-196
< COMPONENT DIAGNOSIS >
[VQ37VHR]
P0128 THERMOSTAT FUNCTION
Component Inspection
INFOID:0000000001910834
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
1 and 2
Temperature
°
C (
°
F)
20 (68)
2.37 - 2.63 k
Ω
50 (122)
0.68 - 1.00 k
Ω
90 (194)
0.236 - 0.260 k
Ω
JMBIA0080ZZ
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