Lexus RX300 (MCU15). Manual — part 204

A09300

Vehicle speed

30 km/h
(19 mph)

Idling(c)

(d)

(e)

(a)

IG SW OFF

(b)

(e)

60 sec.
or more

(f)

(f)

Once
40 sec.
or more

Twice
40 sec.
or more

Nine times
40 sec.
or more

10 sec.

10 sec.

(e)

10 sec.

DI–48

–

DIAGNOSTICS

ENGINE

LEXUS RX300 (RM785E)

DTC

P0136

Oxygen Sensor Circuit Malfunction (Bank 1
Sensor 2)

CIRCUIT DESCRIPTION

Refer to DTC P0125 on page DI–42.

DTC No.

DTC Detecting Condition

Trouble Area

P0136

Voltage output of heated oxygen sensor remains at 0.45 V or

more or 0.55 V or less when vehicle is driven at 100 km/h (62

mph) or more after engine is warmed up (2 trip detection logic)

S Open or short in heated oxygen sensor circuit

S Oxygen sensor

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

WIRING DIAGRAM

Refer to DTC P0125 on page DI–42.

CONFIRMATION DRIVING PATTERN

(a)

Connect the hand–held tester to the DLC3.

(b)

Switch the hand–held tester from the Normal Mode to the Check (Test) Mode
(See page DI–3).

(c)

Start the engine and let the engine idle for 60 seconds or more.

(d)

Drive the vehicle at 30 km/h (19 mph) or more for 40 seconds or more.

(e)

Let the engine idle for 10 seconds or more.

(f)

Preform steps (d) to (e) 9 times.

HINT:
If a malfunction exists, the CHK ENG warning light will be indicated on the multi information display during
step (f).
NOTICE:
If the conditions in this test are not strictly followed, detection of the malfunction will not be possible.
If you do not have a hand–held tester, turn the ignition switch OFF after performing steps (c) to (f),
then perform steps (c) to (f) again.

DI68O–11

–

DIAGNOSTICS

ENGINE

DI–49

LEXUS RX300 (RM785E)

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

Are there any other codes (besides DTC P0136) being output?

YES

Go to relevant DTC chart (See page DI–14).

NO

2

Check for open and short in harness and connector between engine ECU and
oxygen sensor (See page IN–32).

NG

Repair or replace harness or connector.

OK

3

Check output voltage of oxygen sensor.

PREPARATION:
(a)

Connect the hand–held tester to the DLC3.

(b)

Warm up the engine to normal operating temperature.

CHECK:
Read voltage output of the oxygen sensor when the engine suddenly raced.
HINT:
Perform quick racing to 4,000 rpm 3 min. using the accelerator pedal.
OK:

Oxygen sensor output voltage: Alternates from 0.4 V or less to 0.5 V or more.

OK

Check that each connector is properly con-
nected.

NG

Replace oxygen sensor.

A10221

BE6653

A11441

ON

HTS(+)

DI–50

–

DIAGNOSTICS

ENGINE

LEXUS RX300 (RM785E)

DTC

P0141

Oxygen Sensor Heater Circuit
Malfunction (Bank 1 Sensor 2)

CIRCUIT DESCRIPTION

Refer to DTC P0125 on page DI–42.

DTC No.

DTC Detecting Condition

Trouble Area

P0141

When the heater operates, heater current exceeds 2 A

S Open or short in heater circuit of oxygen sensor

O

h

t

P0141

Heater current of 0.2 A or less when the heater operates

S Oxygen sensor heater

S Engine ECU

WIRING DIAGRAM

Refer to DTC P0125 on page DI–42.

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

Check voltage between terminals HT1A, HT1B of engine ECU connector and
body ground.

PREPARATION:
(a)

Remove the engine ECU with connector still connected
(See page FI–70).

(b)

Turn the ignition switch ON.

CHECK:
Measure voltage between terminals HTS of the engine ECU
connector and body ground.
HINT:
OK:

Voltage: 9 – 14 V

OK

Check and replace engine ECU
(See page IN–32).

NG

DI2S8–15

–

DIAGNOSTICS

ENGINE

DI–51

LEXUS RX300 (RM785E)

2

Check resistance of oxygen sensor heater (See page FI–69).

NG

Replace oxygen sensor.

OK

Check and repair harness or connector be-
tween main relay and oxygen sensor and en-
gine ECU (See page IN–32).