Toyota Sequoia (2005). Manual — part 79
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DIAGNOSTICS
ENGINE
DI–119
313
DTC
P0115
Engine Coolant Temperature Circuit
DTC
P0117
Engine Coolant Temperature Circuit Low
Input
DTC
P0118
Engine Coolant Temperature Circuit High
Input
CIRCUIT DESCRIPTION
A thermistor is built in the Engine Coolant Temperature (ECT) sensor and changes the resistance value ac-
cording to the engine coolant temperature.
The structure of the sensor and connection to the ECM is the same as the Intake Air Temperature (IAT) sen-
sor.
HINT:
If the ECM detects the DTC ”P0115, P0117 or P0118”, it operates the fail–safe function in which the ECT
is assumed to be 80
C (176
F).
DTC No.
Proceed to
DTC Detection Condition
Trouble Area
P0115
Step 1
Open or short in engine cool-
ant temperature sensor circuit
for 0.5 sec.
P0117
Step 4
Short in engine coolant tem-
perature sensor circuit for 0.5
sec.
Open or short in engine coolant temperature sensor circuit
Engine coolant temperature sensor
ECM
P0118
Step 2
Open in engine coolant tem-
perature sensor circuit for 0.5
sec.
HINT:
After confirming DTC ”P0115, P0117 or P0118”, use the OBD II scan tool or the hand–held tester to confirm
the engine coolant temperature from the DIAGNOSIS / ENHANCED OBD II / DATA LIST / ALL.
Displayed Temperature
Malfunction
–40
°
C (–40
°
F)
Open circuit
140
°
C (284
°F) or more
Short circuit
MONITOR DESCRIPTION
The ECT (Engine Coolant Temperature) sensor is used to monitor the engine coolant temperature. The ECT
sensor has a thermistor that varies its resistance depending on the temperature of the engine coolant. When
the coolant temperature is low, the resistance in the thermistor increases. When the temperature is high, the
resistance drops. The resistance varies as output voltage from the sensor changes.
The ECM monitors the sensor voltage and uses this value to calculate the engine coolant temperature.
When the sensor output voltage deviates from the normal operating range, the ECM interprets this as a fault
in the ECT sensor and sets a DTC.
DI3HO–13
DI–120
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DIAGNOSTICS
ENGINE
314
Example:
When the ECM calculates that the ECT is less than –40
C (–40
F), or more than 140
C (284
F), and if either
the condition continues for 0.5 sec. or more, the ECM will set a DTC.
MONITOR STRATEGY
P0115
Engine coolant temperature sensor range check
(Fluttering)
Related DTCs
P0117
Engine coolant temperature sensor range check
(Low resistance)
P0118
Engine coolant temperature sensor range check
(High resistance)
Required sensors/components
Engine coolant temperature sensor
Frequency of operation
Continuous
Duration
0.5 sec.
MIL operation
Immediate
Sequence of operation
None
TYPICAL ENABLING CONDITIONS
The monitor will run whenever these
DTCs are not present
See page
The typical enabling condition is not avail-
able
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TYPICAL MALFUNCTION THRESHOLDS
Detection Criteria
Threshold
P0115:
Engine coolant temperature sensor resistance
(Coolant temperature)
Less than 79
Ω,
or more than 156 k
Ω
(More than 140
C (284
F), or less than –40
C (–40
F))
P0117:
Engine coolant temperature sensor resistance
(Coolant temperature)
Less than 79
Ω
(More than 140
C (284
F))
P0118:
Engine coolant temperature sensor resistance
(Coolant temperature)
More than 156 k
Ω
(Less than –40
C (–40
F))
COMPONENT OPERATING RANGE
Parameter
Standard Value
Engine coolant temperature sensor resistance
79
Ω
(140
C (284
F)) to
156 k
Ω
(–40
C (–40
F))
FI6448
ECM
5 V
THW
E2
Engine Coolant Temp. Sensor
2
1
G–Y
G–W
E1
E2
E8
E8
28
21
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DIAGNOSTICS
ENGINE
DI–121
315
WIRING DIAGRAM
INSPECTION PROCEDURE
HINT:
If DTCs related to different system that have terminal E2 as the ground terminal are output simulta-
neously, terminal E2 may have an open circuit.
Read freeze frame data using
the hand−held tester
. Freeze frame data records the engine conditions
when a malfunction is detected. When troubleshooting, freeze frame data can help determine if the
vehicle was running or stopped, if the engine was warmed up or not, if the air–fuel ratio was lean or
rich, as well as other data from the time when a malfunction occurred.
DI–122
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DIAGNOSTICS
ENGINE
316
1
Connect hand–held tester, and read value of engine coolant temperature.
PREPARATION:
(a)
Connect the hand–held tester to the DLC3.
(b)
Turn the ignition switch ON and push the hand–held tester main switch ON.
(c)
When using hand–held tester, enter the following menu: DIAGNOSIS / ENHANCED OBD II / DATA
LIST / ALL / COOLANT TEMP.
CHECK:
Read the temperature value on the the hand–held tester.
OK:
Same value as actual engine coolant temperature.
RESULT:
Displayed Temperature
Proceed to
–40
°
C (–40
°
F)
A
140
°
C (284
°
F) or more
B
OK (Same as present temperature)
C
HINT:
If there is an open circuit, hand–held tester indicates –40
°
C (–40
°
F).
If there is a short circuit, hand–held tester indicates 140
°
C (284
°
F) or more.
B
C
Check for intermittent problems
(See page
A
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