Infiniti Q45 (FY33). Manual — part 158
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SEF594K
Engine Coolant Temperature (ECT) Sensor
COMPONENT DESCRIPTION
The engine coolant temperature sensor is located near the No. 2
injector. The sensor is used to detect the engine coolant tempera-
ture. The sensor modifies a voltage signal from the ECM. The
modified signal returns to the ECM as the engine coolant tempera-
ture 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
<Reference data>
Engine coolant
temperature
°C (°F)
Voltage*
V
Resistance
k
Ω
−10 (14)
4.4
7.0 - 11.4
20 (68)
3.5
2.1 - 2.9
50 (122)
2.2
0.68 - 1.00
90 (194)
1.0
0.236 - 0.260
*: These data are reference values and are measured between ECM terminal
q
67
(Engine coolant temperature sensor) and ground.
CAUTION:
Do not use ECM ground terminals when measuring voltage.
Doing so may result in damage to the ECM’s transistor. Use a
ground other than ECM terminals such as the body ground.
ON BOARD DIAGNOSIS LOGIC
Diagnostic
Trouble
Code No.
Malfunction is detected when ...
Check Items
(Possible Cause)
P0125
0908
I
Voltage sent to ECM from the sensor is not practical,
even when some time has passed after starting the
engine.
I
Engine coolant temperature is insufficient for closed
loop fuel control.
I
Harness or connectors
(High resistance in the circuit)
I
Engine coolant temperature sensor
I
Thermostat
GI
MA
EM
LC
FE
AT
PD
FA
RA
BR
ST
RS
BT
HA
EL
IDX
TROUBLE DIAGNOSIS FOR DTC P0125
EC-161
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SEF399X
DIAGNOSTIC TROUBLE CODE CONFIRMATION
PROCEDURE
CAUTION:
Do not overheat engine.
NOTE:
I
If DTC P0115 (0103) is displayed with P0125 (0908), first
perform TROUBLE DIAGNOSIS FOR DTC P0115, EC-145.
I
If “DIAGNOSTIC TROUBLE CODE CONFIRMATION PRO-
CEDURE” has been previously conducted, always turn
ignition switch “OFF” and wait at least 5 seconds before
conducting the next test.
1) Turn ignition switch “ON”.
2) Select “COOLAN TEMP/S” in “DATA MONITOR” mode
with CONSULT-II.
3) Check that “COOLAN TEMP/S” is above 10°C (50°F).
If it is above 10°C (50°F), the test result will be OK.
If it is below 10°C (50°F), go to following step.
4) 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.
5) If
1st
DTC
is
detected,
go
to
“DIAGNOSTIC
PROCEDURE”, EC-164.
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ OR ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Follow the procedure “With CONSULT-II” above.
TROUBLE DIAGNOSIS FOR DTC P0125
Engine Coolant Temperature (ECT) Sensor
(Cont’d)
EC-162
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TEC642
GI
MA
EM
LC
FE
AT
PD
FA
RA
BR
ST
RS
BT
HA
EL
IDX
TROUBLE DIAGNOSIS FOR DTC P0125
Engine Coolant Temperature (ECT) Sensor
(Cont’d)
EC-163
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SEF052T
SEF541P
SEF542P
DIAGNOSTIC PROCEDURE
INSPECTION START
CHECK POWER SUPPLY.
1. Turn ignition switch “OFF”.
2. Disconnect engine coolant temperature
sensor harness connector.
3. Turn ignition switch “ON”.
4. Check voltage between terminal
q
2
and
ground with CONSULT-II or tester.
Voltage:
Approximately 5V
OK
E
NG
Check the following.
I
Harness connectors
F26
,
F106
I
Harness for open or
short between ECM and
engine coolant tempera-
ture sensor
If NG, repair harness or
connectors.
CHECK GROUND CIRCUIT.
1. Turn ignition switch “OFF”.
2. Check harness continuity between ter-
minal
q
1
and engine ground.
Continuity should exist.
If OK, check harness for short to power.
OK
E
NG
Check the following.
I
Harness connectors
F26
,
F106
I
Harness connectors
F63
,
M49
I
Harness connectors
M4
,
B3
I
Joint connector-16
I
Harness for open or
short between ECM and
engine coolant tempera-
ture sensor
I
Harness for open or
short between TCM
(Transmission Control
Module) and engine
coolant temperature sen-
sor
I
Harness for open or
short between engine
coolant temperature sen-
sor and throttle actuator
control (TAC) module
If NG, repair open circuit or
short to power in harness
or connectors.
CHECK COMPONENT
(Engine coolant temperature sensor).
Refer to “COMPONENT INSPECTION” on
next page.
OK
E
NG
Replace engine coolant
temperature sensor.
CHECK THERMOSTAT OPERATION.
When the engine is cold [lower than 75°C
(167°F)], grasp lower radiator hose and
confirm the engine coolant does not flow.
OK
E
NG
CHECK COMPONENT.
(Thermostat)
Refer to LC section (“Ther-
mostat”).
If NG, replace it.
Perform “TROUBLE DIAGNOSIS FOR
INTERMITTENT INCIDENT”, EC-117.
INSPECTION END
TROUBLE DIAGNOSIS FOR DTC P0125
Engine Coolant Temperature (ECT) Sensor
(Cont’d)
H
H
H
H
H
H
EC-164
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