Lexus ES300 (1997 year). Manual - part 315

A00217

ON

Engine Coolant
Temp. Sensor

ECM

5V

E2

THW

E9 Connector

BE6653
FI7056
FI7034

DI–36

–

DIAGNOSTICS

ENGINE

188

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:Engine coolant temp. sensor 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

).

–

DIAGNOSTICS

ENGINE

DI–37

189

1997 LEXUS ES300   (RM511U)

DTC

P0116

Engine Coolant Temp. Circuit  Range/
Performance problem

CIRCUIT DESCRIPTION

Refer to DTC P0115 (Engine Coolant Temp. Circuit Malfunction) on page 

DI–33

.

DTC No.

DTC Detecting Condition

Trouble Area

P0116

If THW   –7

°

C (19.4

°

F), 20 min. or more after starting

engine, engine coolant temp. sensor value is 35

°

C (95

°

F) or

less

(2 trip detection logic)

Engine coolant temp. sensor

C

li

t

P0116

 If THW   –7

°

C (19.4

°

F), 5 min. or more after starting engine,

engine coolant temp. sensor value is 35

°

C (95

°

F) or less      

(2 trip detection logic)

Cooling system

INSPECTION PROCEDURE

HINT:If DTC P0115 (Engine Coolant Temp. Circuit Malfunction) and P0116 (Engine Coolant Temp. Circuit
Range/Performance) are output simultaneously, engine coolant temp. sensor circuit may be open. 
Perform troubleshooting of DTC P0115 first.

1

Are there any other codes (besides DTC P0116) being output?

YES

 Go to relevant DTC chart. 

NO

2

Check thermostat (See page 

CO–11

).

NG

 Replace thermostat. 

OK

Replace engine coolant temp. sensor.

DI09F–01

P24296

ECM

Throttle Position

Sensor

VC

VTA

E2

DI–38

–

DIAGNOSTICS

ENGINE

190

1997 LEXUS ES300   (RM511U)

DTC

P0120

Throttle/Pedal position Sensor/Switch ”A”
Circuit Malfunction

CIRCUIT DESCRIPTION

The throttle position sensor is mounted in the throttle body and
detects the throttle valve opening angle. When the throttle valve
is fully closed, a voltage of approximately 0.7 V is applied to ter-
minal VTA of the ECM. The voltage applied to the terminals VTA
of the ECM increases in proportion to the opening angle of the
throttle valve and becomes approximately 2.7 

∼

 5.2 V when the

throttle valve is fully opened. The ECM judges the vehicle driv-
ing conditions from these signals input from terminals VTA and
uses them as one of the conditions for deciding the air–fuel ratio
correction, power increase correction and fuel–cut control etc.
 

DTC No.

DTC Detecting Condition

Trouble Area

P0120

Condition (a) or (b) continues:

(a)  VTA    0.1 V

(b)  VTA   4.9 V

Open or short in throttle position sensor circuit

Throttle position sensor

ECM

HINT:After confirming DTC P0120 use the OBD II scan tool or LEXUS hand–held tester to confirm the throttle
valve opening percentage and closed throttle position  switch condition.

Throttle valve opening position

expressed as percentage

Trouble Area

Throttle valve fully closed

Throttle valve fully open

Trouble Area

0 %

0 %

VC line open

VTA line open or short

Approx. 100 %

Approx. 100 %

E2 line open

DI09G–01

S05019

ECM

1

3

2

E9

E9

E9

1

7

22

5V

VC

VTA1

E2

Y

L

BR

Throttle Position Sensor

FI7052

–

DIAGNOSTICS

ENGINE

DI–39

191

1997 LEXUS ES300   (RM511U)

WIRING DIAGRAM

INSPECTION PROCEDURE

HINT:If DTC P0110, P0115, P0120 and P1410 are output simultaneously, E2 (Sensor Ground) may be open.

1

Connect OBD II scan tool or LEXUS hand–held tester, read throttle valve opening
percentage.

PREPARATION:
(a)

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

(b)

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

CHECK:
Read the throttle valve opening percentage.

OK:

Throttle valve

Throttle valve opening position

expressed as percentage

Fully open

Approx.  75 %

Fully closed

Approx.  10 %

OK

 Check for intermittent problems
 (See page 

DI–3

).

NG