NISSAN LATIO 2009 Service Repair Manual

P0125 ECT SENSOR
EC-175
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P0125 ECT SENSOR
Description INFOID:0000000004780096
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 terminal 38
(Engine coolant temperature sensor) and ground.
CAUTION:
Do not use ECM ground terminals when measuring input/output vo ltage. Doing so may result in damage to the ECM's transis-
tor. Use a ground other than ECM terminals, such as the ground.
DTC Logic INFOID:0000000004780097
DTC DETECTION LOGIC NOTE:
• If DTC P0125 is displayed with P0 116, first perform the trouble diagnosis for DTC P0116. Refer to EC-165, " DTC Logic " .
• If DTC P0125 is displayed with P0117 or P0118, fi rst perform the trouble diagnosis for DTC P0117 or
P0118. Refer to EC-167, " DTC Logic " .
DTC CONFIRMATION PROCEDURE 1.
PRECONDITIONING
If DTC Confirmation Procedure has been previously conduc ted, 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. 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 coolant
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

YES >> INSPECTION END
NO >> GO TO 3. YES >>
EC-176, " Diagnosis Procedure "
NO >> INSPECTION END
Diagnosis Procedure INFOID:0000000004780098Ground Inspection " .
Is the inspection result normal? YES >> GO TO 2.
NO >> Repair or replace ground connection. Component Inspection " .
Is the inspection result normal? YES >> GO TO 3.
NO >> Replace engine coolant temperature sensor. YES >> GO TO 4.
NO >> Repair or replace thermostat. Refer to CO-22, " Removal and Installation " .
Diagnosis Procedure " .
>> INSPECTION END
Component Inspection INFOID:0000000004780099

P0125 ECT SENSOR
EC-177
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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 PBIB2005E

EC-178< COMPONENT DIAGNOSIS >
[HR16DE]
P0127 IAT SENSOR
P0127 IAT SENSOR
Description INFOID:0000000004780100
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.
<Reference data>
*: These data are reference values and are measured between ECM terminal 46
(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:0000000004780101
DTC DETECTION LOGIC
DTC CONFIRMATION PROCEDURE 1.
PRECONDITIONING
If DTC Confirmation Procedure has been previously conduc ted, 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 96 °C (205 °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 96 °C (205 °F), turn ignition switch OFF and cool down
engine. 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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NOTE:
Perform the following steps before engine coolant temperature is above 96 °C (205 °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 95 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-179, " Diagnosis Procedure " .
NO >> INSPECTION END
Diagnosis Procedure INFOID:0000000004780102Ground Inspection " .
Is the inspection result normal? YES >> GO TO 2.
NO >> Repair or replace ground connection. Component Inspection " .
Is the inspection result normal? YES >> GO TO 3.
NO >> Replace mass air flow sensor ( with intake air temperature sensor).Diagnosis Procedure " .
>> INSPECTION END
Component Inspection INFOID:0000000004780103YES >> INSPECTION END
NO >> Replace mass air flow sensor ( with intake air temperature sensor).

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 leak in the seal or the thermostat stuck open.
DTC CONFIRMATION PROCEDURE YES >> Go to
EC-180, " Diagnosis Procedure " .
NO >> INSPECTION END
Diagnosis Procedure INFOID:0000000004780105Component Inspection " .
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 engine has run long enough. • Thermostat
• Leakage from sealing portion of thermostat
• Engine coolant temperature sensor VHCL SPEED SE More th
an 56km/h (35MPH)

P0128 THERMOSTAT FUNCTION
EC-181
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Is the inspection result normal? YES >> GO TO 2.
NO >> Replace engine coolant temperature sensor. 2.
CHECK THERMOSTAT
Refer to CO-23, " Inspection " .
Is the inspection result normal? YES >> INSPECTION END
NO >> Replace thermostat.
Component Inspection INFOID:00000000047801061.
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 PBIB2005E

YES >> Go to
EC-185, " Diagnosis Procedure " . PBIB3354E

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NO-1 >> With CONSULT-III: GO TO 3.
NO-2 >> Without CONSULT-III: GO TO 7. YES >> GO TO 4.
NO >> Go to EC-185, " Diagnosis Procedure " .
“ TESTING ” displayed on CONSULT-III screen?
YES >> GO TO 5.
NO >> Check A/F sensor 1 function again. GO TO 3. “ TESTING ” change to?
COMPLETED>>GO TO 6.
OUT OF CONDITION>>Retry DTC CO NFIRMATION PROCEDURE. GO TO 4.YES >> INSPECTION END
NO >> Go to EC-185, " Diagnosis Procedure " .
Component Function Check " .
NOTE:
Use component function check to check the overall function of the A/F sensor 1 circuit. During this check, a
1st trip DTC might not be confirmed.
Is the inspection result normal? YES >> INSPECTION END
NO >> Go to EC-185, " Diagnosis Procedure " .
Component Function Check INFOID:0000000004780109

YES >> Go to
EC-185, " Diagnosis Procedure " .
NO >> INSPECTION END