Toyota Sequoia (2005). Manual - part 80

A19552

Engine Coolant 
Temp. Sensor

2

1

THW

E2

ECM

E2

B17441

Engine Coolant
Temp. Sensor

ECM

E2

THW

E2

THW

E2

E8

ECM Connector

–

DIAGNOSTICS

ENGINE

DI–123

317

2

Check for open in harness or ECM.

PREPARATION:
(a)

Disconnect the E2 engine coolant temperature (ECT)
sensor connector.

(b)

Connect terminals 1 and 2 of the engine coolant tempera-
ture sensor wire harness side connector.

(c)

Turn the ignition switch ON.

(d)

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 hand–held tester.
OK:

Standard: Temperature value: 140

°

C (284

°

F) or more

OK

Confirm good connection at sensor. If OK, re-
place engine coolant temperature sensor.

NG

3

Check for open in harness or ECM.

PREPARATION:
(a)

Disconnect the E2 engine coolant temperature sensor
connector.

(b)

Connect terminals THW and E2 of the E8 ECM connector.

HINT:
Before checking, do a visual and contact pressure checks for
the ECM connector.
(c)

Turn the ignition switch ON.

(d)

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 OBD II scan tool or the
hand–held tester.
OK:

Standard: Temperature value: 140

°

C (284

°

F) or more

OK

Repair or replace harness or connector.

NG

A19550

Engine Coolant
Temp. Sensor

ECM

2

1

E2

THW

E2

B17442

ECM

Engine Coolant
Temp. Sensor

E2

THW

E2

ECM Connector

E8

DI–124

–

DIAGNOSTICS

ENGINE

318

Confirm good connection at ECM. If OK, re-
place ECM (See page 

SF–80

).

4

Check for short in harness and ECM.

PREPARATION:
(a)

Disconnect the E2 engine coolant temperature sensor
connector.

(b)

Turn the ignition 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 hand–held tester.
OK:

Standard: Temperature value: –40

°

C (–40

°

F)

OK

Replace engine coolant temperature sensor.

NG

5

Check for short in harness or ECM.

PREPARATION:
(a)

Disconnect the E8 ECM connector.

(b)

Turn the ignition 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 hand–held tester.
OK:

Standard: Temperature value: –40

°

C (–40

°

F)

OK

Repair or replace harness or connector.

NG

Replace ECM (See page 

SF–80

).

–

DIAGNOSTICS

ENGINE

DI–125

319

DTC

P0116

Engine Coolant Temperature Circuit  Range/
Performance Problem

CIRCUIT DESCRIPTION

Refer to DTC P0115 on page 

DI−119

.

DTC No.

DTC Detecting Condition

Trouble Area

If the engine coolant temperature was 35

°

C (95

°

F) or more but

less than 60

°

C (140

°

F) when the engine is started, and if

conditions (a) and (b) are met:

(a) Vehicle has accelerated and decelerated.

(b) Engine coolant temperature remains within 3

°

C (5.4

°

F) of

the initial engine coolant temperature (2 trip detection logic)

P0116

If the engine coolant temperature is more than 60

°

C (140

°

F)

when the engine is started, and if conditions (a) and (b) are

met:

(a) Vehicle has accelerated and decelerated.

(b) If the engine coolant temperature sensor records a temper-

ature variation below 1

°

C (1.8

°

F) successively 6 times (6

trip detection logic)

Engine coolant temperature sensor

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 variations in resistance are reflected in the voltage output from the sensor. The ECM
monitors the sensor voltage and uses this value to calculate the engine coolant temperature. When the sen-
sor output voltage deviates from the normal operating range, the ECM interprets this as a fault in the ECT
sensor and sets a DTC.
Examples:
(1) Upon starting the engine, the ECT is between 35

°

C (95

°

F) and 60

°

C (140

°

F). If after driving for 250 sec.,

the ECT still remains within 3

°

C (5.4

°

F) of the starting temperature, a DTC will be set (2 trip detection logic).

(2) Upon starting the engine, the ECT is over 60

°

C (140

°

F). If after driving for 250 sec., the ECT still remains

within 1

°

C (1.8

°

F) of the starting temperature, a DTC will be set (6 trip detection logic).

MONITOR STRATEGY

Related DTCs

P0116

Engine coolant temperature sensor range check 
(Stuck)

Main sensors/components

Engine coolant temperature sensor

Required sensors/components

Related sensors/components

Intake air temperature sensor, Crankshaft 
position sensor, Mass air flow meter

Frequency of operation

Continuous

Duration

250 sec.

MIL operation

2 driving cycles (When temperature is fixed between 35



C (95



F) and 60



C (140



F))

6 driving cycles (When temperature is fixed at 60



C (140



F) or more)

Sequence of operation

None

DI3HP–11

DI–126

–

DIAGNOSTICS

ENGINE

320

TYPICAL ENABLING CONDITIONS

It

Specification

Item

Minimum

Maximum

The monitor will run whenever this DTC is
not present

See page  

DI–18

Case 1 (When temperature is fixed between 35



C (95



F) and 60



C (140



F)):

Cumulative idle off period

250 sec.

–

Speed increase 30 km/h (18.6 mph) or
more

10 times

–

Engine coolant temperature

35



C (95



F)

60



C (140



F)

Intake air temperature

–6.7



C (20



F)

–

Case 2 (When temperature is fixed at 60



C (140



F) or more):

Engine coolant temperature at engine
start

60



C (140



F)

–

Intake air temperature

–6.7



C (20



F)

–

Stop and go

Once or more (Stop for 20 sec. or more and accelerate to more than 70 km/h (43.5 mph) 

with in 40 sec.)

Steady driving and stop *

Once or more

*: Vehicle is driven by 65 km/h (40.4 mph) or more for 30 sec. or more and the vehicle speed reaches 70
km/h (43.5 mph). The vehicle is decelerated from 65 km/h (40.4 mph) to 3 km/h (1.86 mph) or less within
35 sec. and stopped for 10 sec.

TYPICAL MALFUNCTION THRESHOLDS

Detection Criteria

Threshold

Case1 (When temperature is fixed between 35



C (95



F) and 60



C (140



F)):

Change of engine coolant temperature value

Less than 3



C (5.4



F)

Case2 (When temperature is fixed at 60



C (140



F) or more):

Change of engine coolant temperature value

1



C (1.8



F) or less

COMPONENT OPERATING RANGE

Standard Value

Engine coolant temperature changes with the actual engine coolant temperature.

INSPECTION PROCEDURE

HINT:

If DTC P0115, P0116, P0117, P0118 and P0125 are output simultaneously, ECT sensor circuit may
be open or shorted. Perform the troubleshooting of DTC P0115, P0117 or P0118 first.

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.

Replace engine coolant temperature sensor.