Lexus ES300 (2002 year). Service manual - part 360

A61585

Engine 
Room 
R/B

21

1

Battery

FL MAIN

B-G

E.F.I. 
ECU 
Relay

2

1A

1C

1B

1K

E.F.I.

B-W

Heated Oxygen 
Sensor (B1S2)

ED

J11 J/C

A

BR

+B

OX

HT

E1

E1

E6

E8

EF

E8

E9

OX1B

HT1B

OX2B

HT2B

MREL

(*1)

ECM

E1

B-G

1

Engine Room J/B

E8

E9

6

29

5

8

1

BR

OX

+B

HT

A

A

(*1)

6

2

1

5

3

2

3

1

4

3

4

2

1

W

L

B

Y

Heated Oxygen 
Sensor (B2S2)

W-B

B-W

B-W

*1: Shielded

EF

A

BR

BR

BR

BR

5

3

BR

05-60

-

DIAGNOSTICS

SFI SYSTEM (1MZ-FE)

213

2002 LEXUS ES300 REPAIR MANUAL   (RM911U)

WIRING DIAGRAM

A56997

Bank 1

Bank 2

HT

+B

OX

E1

HT

+B

OX

E1

A55005

OX1B

OX2B

E2

E9

-

DIAGNOSTICS

SFI SYSTEM (1MZ-FE)

05-61

214

2002 LEXUS ES300 REPAIR MANUAL   (RM911U)

INSPECTION PROCEDURE

NOTICE:
If the vehicle run out of fuel, the air-fuel ratio becomes LEAN and DTC P0125 will be recorded. and
the check engine warning light then comes on.
HINT:
Read freeze frame data using hand-held tester. Because freeze frame records the engine conditions when
the malfunction is detected, when troubleshooting it is useful for determining whether the vehicle was run-
ning or stopped, the engine warmed up or not, the air-fuel ratio lean or rich, etc. at the time of the malfunction.

1

CHECK OTHER DTC OUTPUT(BESIDES DTC P0136, P0156)

(a)

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

YES

GO TO RELEVANT DTC CHART

NO

2

CHECK HARNESS AND CONNECTOR(ECM - OXYGEN SENSOR)

(a)

Disconnect the oxygen sensor connector.

(b)

Disconnect the ECM E9 connector.

(c)

Check continuity between the terminals OX1B and OX2B
of the ECM connector and OX of the oxygen sensor con-
nector.
Resistance: 1 

Ω

 or less

(d)

Check for short between the terminals OX1B, OX2B and
E2 of the ECM connector.
Resistance: 1 M

Ω

 or more

NG

REPAIR OR REPLACE HARNESS AND
CONNECTOR

OK

3

READ VALUE OF OBD II SCAN TOOL OR HAND-HELD TESTER(OXIGEN
SENSOR)

(a)

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

(b)

Warm up the engine to normal operating temperature.

(c)

Read the voltage output of the heated oxygen sensor when the engine is suddenly raced.

HINT:
Perform quick racing to 4,000 rpm 3 min. using the accelerator pedal.

Heated oxygen sensor output voltage: Alternates from 0.4 V or less to 0.6 V or more.

05-62

-

DIAGNOSTICS

SFI SYSTEM (1MZ-FE)

215

2002 LEXUS ES300 REPAIR MANUAL   (RM911U)

OK

CHECK THAT EACH CONNECTOR IS
PROPERLY CONNECTED

NG

REPLACE OXYGEN NO.2 SENSOR

A53763

HT1B HT2B

E2

-

DIAGNOSTICS

SFI SYSTEM (1MZ-FE)

05-63

216

2002 LEXUS ES300 REPAIR MANUAL   (RM911U)

DTC

P0141

OXYGEN SENSOR HEATER CIRCUIT
MALFUNCTION (BANK 1 SENSOR 2)

DTC

P0161

OXYGEN SENSOR HEATER CIRCUIT
MALFUNCTION (BANK 2 SENSOR 2)

CIRCUIT DESCRIPTION

Refer to DTC P0125 on page 

05-52

.

DTC No.

DTC Detecting Condition

Trouble Area

P0141
P0161

When the heater operates, heater current exceeds 2.35 A
(2 trip detection logic)

Heater current of 0.2 A or less when the heater operates
(2 trip detection logic)

Open or short in heater circuit of oxygen sensor

Oxygen sensor heater

ECM

HINT:

Bank 1 refers to the bank that includes cylinder No. 1.

Bank 2 refers to the bank that does not include cylinder No. 1.

Sensor 1 refers to the sensor closer to the engine body.

Sensor 2 refers to the sensor farther away from the engine body.

WIRING DIAGRAM

Refer to DTC P0136 on page 

05-59

.

INSPECTION PROCEDURE

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

1

INSPECT ECM

(a)

Turn the ignition switch ON.

(b)

Measure voltage between the terminals HT1B, HT2B and
E2 of the ECM connector.
Voltage: 9 - 14 V

OK

CHECK AND REPLACE ECM

NG

055C6-03