Lexus ES300 (1997 year). Manual — part 314

A00213

ON

Intake Air
Temp. Sensor

E9 Connector

ECM

5V

E2

THA

BE6653
FI7056
FI7034

DI–32

–

DIAGNOSTICS

ENGINE

184

1997 LEXUS ES300 (RM511U)

5

Check for short in harness or ECM.

PREPARATION:
(a)

Remove the glove compartment (See page

SF–64

).

(b)

Disconnect the E9 connector of ECM.

HINT:Mass air flow meter connector is disconnected.
(c)

Turn ignition switch ON.

CHECK:
Read temp. value on the OBD II scan tool or LEXUS hand–held
tester.
OK:

Temp. value: – 40

°

C (– 40

°

F)

OK

Repair or replace harness or connector.

NG

Check and replace ECM (See page

IN–27

).

FI6448

Engine Coolant Temp. Sensor

ECM

5V

THW

E2

E1

20

22

2

1

G–B

BR

E9

E9

–

DIAGNOSTICS

ENGINE

DI–33

185

1997 LEXUS ES300 (RM511U)

DTC

P0115

Engine Coolant Temp. Circuit Malfunction

CIRCUIT DESCRIPTION

A thermistor built into the engine coolant temp. sensor changes the resistance value according to the engine
coolant temp.
The structure of the sensor and connection to the ECM is the same as in the intake air temp. circuit malfunc-
tion shown on page

DI–28

.

If the ECM detects the DTC P0115, it operates the fail–safe function in which the engine coolant temp. is
assumed to be 80

°

C (176

°F).

DTC No.

Detection Item

Trouble Area

P0115

Open or short in engine coolant temp. sensor circuit

Open or short in engine coolant temp. sensor circuit

Engine coolant temp. sensor

ECM

HINT:After confirming DTC P0115 use the OBD II scan tool or LEXUS hand–held tester to confirm the engine
coolant temp. from CURRENT DATA.

Temp. Displayed

Malfunction

–40

°

C (–40

°

F)

Open circuit

140

°C

(284

°F) or more

Short circuit

WIRING DIAGRAM

DI09E–01

A00214

ON

Engine Coolant
Temp. Sensor

ECM

5V

E2

20

22

2

1

THW

BE6653
FI7055

E9

E9

DI–34

–

DIAGNOSTICS

ENGINE

186

1997 LEXUS ES300 (RM511U)

INSPECTION PROCEDURE

HINT:If DTC P0110 (Intake Air Temp. Circuit Malfunction), P0115 (Engine Coolant Temp. Circuit Malfunc-
tion), P0120 (Throttle/Pedal/Position Sensor/Switch ”A” Circuit Malfunction) and P1410 (EGR Valve Position
Sensor Circuit Malfunction) are output simultaneously, E2 (Sensor Ground) may be open.

1

Connect OBD II scan tool or LEXUS hand–held tester, and read value of
engine coolant temp.

PREPARATION:
(a)

Connect the OBD II scan tool or LEXUS hand–held tester to the DLC3.

(b)

Turn ignition switch ON and switch the OBD II scan tool or LEXUS hand–held tester main switch ON.

CHECK:
Read temp. value on the OBD II scan tool or LEXUS hand–held tester.
OK:

Same as actual engine coolant temp.

HINT:

If there is open circuit, OBD II scan tool or LEXUS hand–held tester indicates –40

°

C (–40

°F).

If there is open circuit, OBD II scan tool or LEXUS hand−held tester indicates

140

°

C (284

°F) or more.

NG

–40

°

C (–40

°

F) ... Go to step 2.

140

°

C (284

°

F) or more ... Go to step 4.

OK

Check for intermittent problems
(See page

DI–3

).

2

Check for open in harness or ECM.

PREPARATION:
(a)

Disconnect the engine coolant temp. sensor connector.

(b)

Connect sensor wire harness terminals together.

(c)

Turn ignition switch ON.

CHECK:
Read temp. value on the OBD II scan tool or LEXUS hand–held
tester.
OK:

Temp. value: 140

°

C (284

°

F) or more

OK

Confirm good connection at sensor.
If OK, replace engine coolant temp. sensor.

NG

A00215

ON

Engine Coolant
Temp. Sensor

E2

THW

ECM

5V

E2

2

1

20

22

E9

E9

BE6653
FI7057
P20200

THW

A00216

ON

Engine Coolant
Temp. Sensor

ECM

5V

E2

20

22

E9

E9

THW

FI7054

BE6653

–

DIAGNOSTICS

ENGINE

DI–35

187

1997 LEXUS ES300 (RM511U)

3

Check for open in harness or ECM.

PREPARATION:
(a)

Remove the glove compartment (See page

SF–64

).

(b)

Connect between terminals THW and E2 of ECM connec-
tor.

HINT:Engine coolant temp. sensor connector is disconnected.
Before checking, do a visual and contact pressure check for the
ECM connector (See page

IN–27

).

(c)

Turn ignition switch ON.

CHECK:
Read temp. value on the OBD II scan tool or LEXUS hand–held
tester.
OK:

Temp. value: 140

°

C (284

°

F) or more

OK

Open in harness between terminal E2 or THW,
repair or replace harness.

NG

Confirm good connection at ECM.
If OK, check and replace ECM.

4

Check for short in harness and ECM.

PREPARATION:
(a)

Disconnect the engine coolant temp. sensor connector.

(b)

Turn ignition switch ON.

CHECK:
Read temp. value on the OBD II scan tool or LEXUS hand–held
tester.
OK:

Temp. value: –40

°

C (–40

°

F)

OK

Replace engine coolant temp. sensor.

NG