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 

DI–18

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

Go to step 4.

C

Check for intermittent problems 
(See page 

DI–11

).

A