Lexus ES300 (2002 year). Service manual - part 381

A62012

Battery

FL MAIN

B-G

Engine Room R/B

1

1A

1B

ETCS

L-R

+BM

ECM

IL2

1

B-G

2

2

Engine Room J/B

1

6

E7

L-R

L-R

1H

4

1K

9

Engine Room J/B

05-130

-

DIAGNOSTICS

SFI SYSTEM (1MZ-FE)

283

2002 LEXUS ES300 REPAIR MANUAL   (RM911U)

DTC

P1127

ETCS ACTUATOR POWER SOURCE
CIRCUIT MALFUNCTION

CIRCUIT DESCRIPTION

Battery positive voltage is supplied to terminal +BM of the ECM even once when the ignition switch is OFF
for the electric throttle control system.
If this DTC is stored, the ECM shuts down the power for the throttle motor, and the throttle valve is fully closed
by the return spring.

DTC No.

DTC Detection Condition

Trouble Area

P1127

Open in ETCS power source circuit

Open in ETCS power source circuit

ECM

WIRING DIAGRAM

055CN-03

A59660

ETCS(10A)

A53769

+BM

ME01

-

DIAGNOSTICS

SFI SYSTEM (1MZ-FE)

05-131

284

2002 LEXUS ES300 REPAIR MANUAL   (RM911U)

INSPECTION PROCEDURE

HINT:
Read freeze frame data using hand-held tester or OBD II scan tool. Because freeze frame records the en-
gine conditions when the malfunction is detected. When troubleshooting, it is useful for determining whether
the vehicle was running or stopped, the engine was warmed up or not, the air-fuel ratio was lean or rich,
etc. at the time of the malfunction.

1

INSPECT ETCS FUSE

(a)

Check the countinuity of the ETCS fuse.
Standard: Continuity

NG

CHECK FOR SHORT IN ALL THE HARNESS TO
ETCS FUSE

OK

2

INSPECT ECM(+BM - ME01)

(a)

Measure the voltage between terminals +BM and ME01
of the ECM connectors.
Voltage: 9 - 14 V

NG

CHECK AND REPLACE ECM

OK

3

CHECK HARNESS AND CONNECTOR(BATTERY - ETCS FUSE, ETCS FUSE -
ECM)

NG

REPAIR OR REPLACE HARNESS AND
CONNECTOR

OK

CHECK AND REPLACE ECM

A57007

05-132

-

DIAGNOSTICS

SFI SYSTEM (1MZ-FE)

285

2002 LEXUS ES300 REPAIR MANUAL   (RM911U)

DTC

P1128

THROTTLE CONTROL MOTOR LOCK
MALFUNCTION

CIRCUIT DESCRIPTION

Throttle motor is operated by the ECM and it opens and closes the throttle valve. The opening angle of the
throttle valve is detected by the throttle position sensor which is mounted on the throttle body and it provides
feedback to the ECM to control the throttle motor in order the throttle valve opening angle properly in re-
sponse to driving condition. If this DTC is stored, the ECM shuts down the power for the throttle motor, and
the throttle valve is fully closed by the return spring.

DTC No.

DTC Detection Condition

Trouble Area

P1128

Lock throttle control motor during control throttle control motor

Throttle body assy (Throttle motor)

Throttle body assy (Throttle valve)

INSPECTION PROCEDURE

HINT:
Read freeze frame data using hand-held tester or OBD II scan tool, as freeze frame data records the engine
conditions when a malfunction is detected. When troubleshooting, it is useful for determining whether the
vehicle was running or stopped, the engine was warmed up or not, the air-fuel ratio was lean or rich, etc.
at the time of the malfunction.

1

INSPECT THROTTLE BODY ASSY(THROTTLE CONTROL MOTOR)

(a)

Disconnect the throttle control motor connector.

(b)

Using an ohmmeter, measure the motor resistance be-
tween terminals 1 (M-) and 2 (M+).
Motor resistance: 0.3 - 100 

Ω

 at 20

°

C (68

°

F)

NG

REPLACE THROTTLE BODY ASSY

OK

2

INSPECT THROTTLE BODY ASSY(THROTTLE VALVE)

Check whether or not a foreign body is caught between the throttle valve and housing.

NG

REMOVE FOREIGN BODY AND CLEAN
THROTTLE BODY

OK

REPLACE THROTTLE BODY ASSY (See page 

10-6

)

055CA-03

-

DIAGNOSTICS

SFI SYSTEM (1MZ-FE)

05-133

286

2002 LEXUS ES300 REPAIR MANUAL   (RM911U)

DTC

P1129

ELECTRIC THROTTLE CONTROL SYSTEM
MALFUNCTION

CIRCUIT DESCRIPTION

Electric Throttle Control System (ETCS) is composed of the throttle motor to operate the throttle valve, the
throttle position sensor to detect the opening angle of the throttle valve, the accelerator pedal position sensor
to detect the accelerator pedal position, the ECM to control the ETCS and the one valve type throttle body.
The ECM controls the throttle motor to make the throttle valve opening angle properly in response driving
condition.
The throttle position sensor which is mounted on the throttle body detects the opening angle of the throttle
valve, and it provides feedback to the ECM to control the throttle motor.
If the ETCS has a malfunction, the ECM shuts down the power for the throttle motor, and the throttle valve
is fully closed by the return spring.

DTC No.

DTC Detection Condition

Trouble Area

P1129

Throttle opening angle continues to vary greatly from target

throttle opening angle

Electric throttle control system

ECM

WIRING DIAGRAM

Refer to DTC P1125 on page 

05-127

.

INSPECTION PROCEDURE

HINT:
Read freeze frame data using hand-held tester or OBD II scan tool. Because freeze frame records the en-
gine conditions when the malfunction is detected. When troubleshooting, it is useful for determining whether
the vehicle was running or stopped, the engine was warmed up or not, the air-fuel ratio was lean or rich,
etc. at the time of the malfunction.

1

CHECK OTHER DTC OUTPUT(BESIDES DTC P1129)

(a)

Read the DTC using hand-held tester or OBD II scan tool.

YES

GO TO RELEVANT DTC CHART

NO

2

INSPECT THROTTLE BODY ASSY (See Page 

10-1

)

NG

REPLACE THROTTLE BODY ASSY

OK

INSPECT ECM

056H9-01