2001 INFINITI QX4 engine coolant

DescriptionNBEC0081NOTE:
If DTC P0125 is displayed with P0115, first perform the trouble
diagnosis for DTC P0115. Refer to EC-169.
SEF594K
COMPONENT DESCRIPTIONNBEC0081S01The 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 thermistor decreases as temperature increases.
SEF012P

Engine coolant
temperature ÉC (ÉF)Voltage* V Resistance kW
þ10 (14) 4.4 9.2
20 (68) 3.5 2.1 - 2.9
50 (122) 2.2 0.68 - 1.00
90 (194) 0.9 0.236 - 0.260
*: These data are reference values and are measured between ECM terminal 70
(Engine coolant 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.
On Board Diagnosis LogicNBEC0082Malfunction is detected when voltage sent to ECM from the sen-
sor is not practical, even when some time has passed after start-
ing the engine, or engine coolant temperature is insufficient for
closed loop fuel control.
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DTC P0125 ENGINE COOLANT TEMPERATURE SENSOR (ECTS)
Description
EC-187

Possible CauseNBEC0431IHarness or connectors
(High resistance in the circuit)
IEngine coolant temperature sensor
IThermostat
SEF174Y
DTC Confirmation ProcedureNBEC0083CAUTION:
Be careful not to overheat engine.
NOTE:
If ªDTC Confirmation Procedureº has been previously conducted,
always turn ignition switch ªOFFº and wait at least 10 seconds
before conducting the next test.
WITH CONSULT-IINBEC0083S011) Turn ignition switch ªONº.
2) Select ªDATA MONITORº mode with CONSULT-II.
3) Check that ªCOOLAN TEMP/Sº is above 10ÉC (50ÉF).
If it is above 10ÉC (50ÉF), the test result will be OK.
If it is below 10ÉC (50ÉF), go to following step.
4) Start engine and run it for 65 minutes at idle speed.
If ªCOOLAN TEMP/Sº increases to more than 10ÉC (50ÉF)
within 65 minutes, stop engine because the test result will
be OK.
5) If 1st trip DTC is detected, go to ªDiagnostic Procedureº,
EC-190.
WITH GSTNBEC0083S02Follow the procedure ªWITH CONSULT-IIº above.
DTC P0125 ENGINE COOLANT TEMPERATURE SENSOR (ECTS)
Possible Cause
EC-188

Wiring DiagramNBEC0084
MEC945C
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DTC P0125 ENGINE COOLANT TEMPERATURE SENSOR (ECTS)
Wiring Diagram
EC-189

Diagnostic ProcedureNBEC0085
1 CHECK ECTS POWER SUPPLY CIRCUIT
1. Turn ignition switch ªOFFº.
2. Disconnect engine coolant temperature sensor harness connector F112, F28.
SEF370Z
3. Turn ignition switch ªONº.
4. Check voltage between ECTS harness connector F28 terminal 3 and ground with CONSULT-II or tester.
SEF371Z
OK or NG
OK©GO TO 3.
NG©Repair open circuit or short to ground or short to power in harness or connectors.
2 DETECT MALFUNCTIONING PART
Check the following.
IHarness connectors F112, F28
IHarness for open or short between ECM and engine coolant temperature sensor
©Repair harness or connectors.
3 CHECK ECTS GROUND CIRCUIT FOR OPEN AND SHORT
1. Turn ignition switch ªOFFº.
2. Check harness continuity between ECTS terminal 2 and engine ground.
Refer to Wiring Diagram.
Continuity should exist.
3. Also check harness for short to power.
OK or NG
OK©GO TO 5.
NG©GO TO 4.
DTC P0125 ENGINE COOLANT TEMPERATURE SENSOR (ECTS)
Diagnostic Procedure
EC-190

4 DETECT MALFUNCTIONING PART
Check the following.
IHarness connectors F112, F28
IHarness for open between ECM and engine coolant temperature sensor
IHarness for open between TCM (Transmission Control Module) and engine coolant temperature sensor
©Repair open circuit or short to power in harness or connectors.
5 CHECK ENGINE COOLANT TEMPERATURE SENSOR
Check resistance between engine coolant temperature sensor terminals 1 and 2 as shown in the figure.
SEF304X
OK or NG
OK©GO TO 6.
NG©Replace engine coolant temperature sensor.
6 CHECK THERMOSTAT OPERATION
When the engine is cold [lower than 70ÉC (158ÉF)] condition, grasp lower radiator hose and confirm the engine coolant
does not flow.
OK or NG
OK©GO TO 7.
NG©Repair or replace thermostat. Refer to LC-16, ªThermostatº.
7 CHECK INTERMITTENT INCIDENT
Refer to ªTROUBLE DIAGNOSIS FOR INTERMITTENT INCIDENTº, EC-140.
©INSPECTION END
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DTC P0125 ENGINE COOLANT TEMPERATURE SENSOR (ECTS)
Diagnostic Procedure (Cont'd)
EC-191

SEF751UA
Component DescriptionNBEC0177The fuel tank temperature sensor is used to detect the fuel tem-
perature inside the fuel tank. The sensor modifies a voltage signal
from the ECM. The modified signal returns to the ECM as the fuel
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.
SEF012P

Fuel temperature
ÉC (ÉF)Voltage* V Resistance kW
20 (68) 3.5 2.3 - 2.7
50 (122) 2.2 0.79 - 0.90
*: These data are reference values and are measured between ECM terminal 92
(Fuel tank temperature sensor) and body 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.
On Board Diagnosis LogicNBEC0178Malfunction is detected when an excessively high or low voltage is
sent to ECM, rationally incorrect voltage is sent to ECM, compared
with the voltage signals from engine coolant temperature sensor
and intake air temperature sensor.
Possible CauseNBEC0489IHarness or connectors
(The sensor circuit is open or shorted.)
IFuel tank temperature sensor
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DTC P0180 FUEL TANK TEMPERATURE SENSOR
Component Description
EC-309

On Board Diagnosis LogicNBEC0610This diagnosis checks whether the engine coolant temperature is
extraordinary high, even when the load is not heavy.
When malfunction is detected, the malfunction indicator lamp (MIL)
will light up even in the first trip.
Malfunction is detected when engine coolant temperature is exces-
sively high under normal engine speed.
Possible CauseNBEC0611IThermostat
IImproper ignition timing
IEngine coolant temperature sensor
IBlocked radiator
IBlocked front end (Improper fitting of nose mask)
ICrushed vehicle frontal area (Vehicle frontal is collided but not
repaired)
IBlocked air passage by improper installation of front fog lamp
or fog lamps.
IImproper mixture ratio of coolant
IDamaged bumper
For more information, refer to ªMAIN 12 CAUSES OF
OVERHEATINGº, EC-319.
Overall Function CheckNBEC0612Use this procedure to check the overall function of the coolant
overtemperature enrichment protection check, a DTC might not be
confirmed.
WARNING:
Never remove the radiator cap when the engine is hot. Serious
burns could be caused by high-pressure fluid escaping from
the radiator.
Wrap a thick cloth around the cap. Carefully remove the cap
by turning it a quarter turn to allow built-up pressure to
escape. Then turn the cap all the way off.
SEF621W
WITH CONSULT-IINBEC0612S011) Check the coolant level and mixture ratio (using coolant tester)
in the reservoir tank and radiator.
Allow engine to cool before checking coolant level and
mixture ratio.
IIf the coolant level in the reservoir and/or radiator is below the
proper range, go to ªDiagnostic Procedureº, EC-316.
IIf the coolant mixture ratio is out of the range of 45 to 55%,
replace the coolant in the following procedure MA-14, ªChang-
ing Engine Coolantº.
a) Fill radiator with coolant up to specified level with a filling speed
DTC P0217 COOLANT OVERTEMPERATURE ENRICHMENT PROTECTION
On Board Diagnosis Logic
EC-314

of 2 liters per minute like pouring coolant from a kettle. Be sure
to use coolant with the proper mixture ratio. Refer to MA-12,
ªAnti-freeze Coolant Mixture Ratioº.
b) After refilling coolant, run engine to ensure that no water-flow
noise is emitted.
c) After checking or replacing coolant, go to step 3 below.
2) Ask the customer if engine coolant has been added. If it has
been added, go to ªDiagnostic Procedureº, EC-316. After
repair, go to the next step.
3) Start engine and let it idle.
4) Make sure that A/C switch is ªOFFº and air conditioner is not
operating. If NG, check air conditioner circuit. Refer to HA-30
or HA-35, ªTROUBLE DIAGNOSESº. After repair, go to the
next step.
5) Check for blocked coolant passage.
a) Warm up engine to normal operating temperature, then grasp
radiator upper hose and lower hose and make sure that cool-
ant flows.
If NG, go to ªDiagnostic Procedureº, EC-316. After repair, go
to the next step.
Be extremely careful not to touch any moving or adjacent
parts.
6) Check for blocked radiator air passage.
a) When market fog lamps have been installed, check for dam-
aged fans and clogging in the condenser and radiator.
b) Check the front end for clogging caused by insects or debris.
c) Check for improper fitting of front-end cover, damaged radia-
tor grille or bumper, damaged vehicle front.
If NG, take appropriate action and then go to the next step.
7) Check function of ECT sensor.
Refer to step 7 of ªDiagnostic Procedureº, EC-316.
If NG, replace ECT sensor and go to the next step.
8) Check ignition timing. Refer to basic inspection, EC-101.
Make sure that ignition timing is 15ɱ5É at idle.
If NG, adjust ignition timing and then recheck.
WITH GSTNBEC0612S021) Check the coolant level and mixture ratio (using coolant tester)
in the reservoir tank and radiator.
Allow engine to cool before checking coolant level and
mixture ratio.
IIf the coolant level in the reservoir and/or radiator is below the
proper range, and go to ªDiagnostic Procedureº, EC-316.
IIf the coolant mixture ratio is out of the range of 45 to 55%,
replace the coolant in the following procedure MA-14, ªChang-
ing Engine Coolantº.
a) Fill radiator with coolant up to specified level with a filling speed
of 2 liters per minute like pouring coolant from a kettle. Be sure
to use coolant with the proper mixture ratio. Refer to MA-12,
ªAnti-freeze Coolant Mixture Ratioº.
b) After refilling coolant, run engine to ensure that no water-flow
noise is emitted.
c) After checking or replacing coolant, go to step 3 below.
2) Ask the customer if engine coolant has been added. If it has
been added, go to ªDiagnostic Procedureº, EC-316. After
repair, go to the next step.
3) Start engine and let it idle.
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DTC P0217 COOLANT OVERTEMPERATURE ENRICHMENT PROTECTION
Overall Function Check (Cont'd)
EC-315