Infiniti EX35. Manual — part 609
EC-178
< COMPONENT DIAGNOSIS >
[VQ35HR]
P0125 ECT SENSOR
P0125 ECT SENSOR
Description
INFOID:0000000003133341
The engine coolant temperature sensor is used to detect the engine
coolant temperature. The sensor modifies a voltage signal from the
ECM. The modified signal returns to the ECM as the engine coolant
temperature input. The sensor uses a thermistor which is sensitive to
the change in temperature. The electrical resistance of the ther-
mistor decreases as temperature increases.
<Reference data>
*: These data are reference values and are measured between ECM terminals 71
(Engine coolant temperature sensor) and 84 (Sensor ground).
DTC Logic
INFOID:0000000003133342
DTC DETECTION LOGIC
NOTE:
If DTC P0125 is displayed with P0117 or P0118, first perform the trouble diagnosis for DTC P0117 ,
P0118. Refer to
DTC CONFIRMATION PROCEDURE
1.
PRECONDITIONING
If DTC Confirmation Procedure has been previously conducted, always turn ignition switch OFF and wait at
least 10 seconds before conducting the next test.
>> GO TO 2.
2.
CHECK ENGINE COOLANT TEMPERATURE SENSOR FUNCTION
With CONSULT-III
1.
Turn ignition switch ON.
2.
Select “DATA MONITOR” mode with CONSULT-III.
3.
Check that “COOLAN TEMP/S” is above 10
°
C (50
°
F).
With GST
Follow the procedure “With CONSULT-III” above.
Is it above 10
°
C (50
°
F)?
SEF594K
Engine coolant temperature
[
°
C (
°
F)]
Voltage*
(V)
Resistance
(k
Ω
)
–10 (14)
4.4
7.0 - 11.4
20 (68)
3.5
2.37 - 2.63
50 (122)
2.2
0.68 - 1.00
90 (194)
0.9
0.236 - 0.260
SEF012P
DTC No.
Trouble diagnosis name
DTC detecting condition
Possible cause
P0125
Insufficient engine cool-
ant temperature for
closed loop fuel control
• Voltage sent to ECM from the sensor is not
practical, even when some time has passed
after starting the engine.
• Engine coolant temperature is insufficient for
closed loop fuel control.
• Harness or connectors
(High resistance in the circuit)
• Engine coolant temperature sensor
• Thermostat
P0125 ECT SENSOR
EC-179
< COMPONENT DIAGNOSIS >
[VQ35HR]
C
D
E
F
G
H
I
J
K
L
M
A
EC
N
P
O
YES
>> INSPECTION END
NO
>> GO TO 3.
3.
PERFORM DTC CONFIRMATION PROCEDURE
With CONSULT-III
1.
Start engine and run it for 65 minutes at idle speed.
If “COOLAN TEMP/S” increases to more than 10
°
C (50
°
F) within 65 minutes, stop engine because
the test result will be OK.
CAUTION:
Be careful not to overheat engine.
2.
Check 1st trip DTC.
With GST
Follow the procedure “With CONSULT-III” above.
Is 1st trip DTC detected?
YES
>>
NO
>> INSPECTION END
Diagnosis Procedure
INFOID:0000000003133343
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 ENGINE COOLANT TEMPERATURE SENSOR
EC-179, "Component Inspection"
Is the inspection result normal?
YES
>> GO TO 3.
NO
>> Replace engine coolant temperature sensor.
3.
CHECK THERMOSTAT OPERATION
When the engine is cold [lower than 70
°
C (158
°
F)] condition, grasp lower radiator hose and confirm the engine
coolant does not flow.
Is the inspection result normal?
YES
>> GO TO 4.
NO
>> Repair or replace thermostat. Refer to
CO-21, "Removal and Installation"
4.
CHECK INTERMITTENT INCIDENT
GI-38, "Intermittent Incident"
.
>> INSPECTION END
Component Inspection
INFOID:0000000003133344
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.
EC-180
< COMPONENT DIAGNOSIS >
[VQ35HR]
P0125 ECT 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
P0127 IAT SENSOR
EC-181
< COMPONENT DIAGNOSIS >
[VQ35HR]
C
D
E
F
G
H
I
J
K
L
M
A
EC
N
P
O
P0127 IAT SENSOR
Description
INFOID:0000000003133345
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 terminals 67
(Intake air temperature sensor) and 68 (Sensor ground).
DTC Logic
INFOID:0000000003133346
DTC DETECTION LOGIC
DTC CONFIRMATION PROCEDURE
1.
PRECONDITIONING
If DTC Confirmation Procedure has been previously conducted, always turn ignition switch OFF and wait at
least 10 seconds before conducting the next test.
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.
-
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).
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
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