Lexus RX300 (MCU15). Manual - part 210

A00479

Engine Speed

3,000 rpm

2,000 rpm

Idling

IG Switch OFF

(a)

Warmed Up

3 min. or so

2 sec.

Check

Time

2 sec.

(b)

(c)

(d)

DI–72

–

DIAGNOSTICS

ENGINE

LEXUS RX300   (RM785E)

CONFIRMATION ENGINE RACING PATTERN

(a)

Connect the hand–held tester to the DLC3.

(b)

Start engine and warm it up with all accessories switched OFF until water temp. is stable.

(c)

Race the engine at 2,500 – 3,000 rpm for about 3 min.

(d)

When racing the engine at 3,000 rpm for 2 sec. and 2,000 rpm for 2 sec. alternately, check the wave-
form of the oxygen sensor (bank 1 sensor 2).

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 was warmed up or not, the air–fuel ratio was lean or rich, etc. at the time of the
malfunction.

1

Are there any other codes (besides DTC P0420) being output?

YES

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

NO

2

Check gas leakage on exhaust system.

NG

Repair or replace.

OK

–

DIAGNOSTICS

ENGINE

DI–73

LEXUS RX300   (RM785E)

3

Check A/F sensor (bank 1 sensor 2) (See page FI–67).

NG

Repair or replace.

OK

4

Check oxygen sensor (bank 1 sensor 2) (See page FI–69).

NG

Repair or replace.

OK

Replace three–way catalytic converter.

A14515

8

E9

Engine ECU

F11 
Fusible Link Block

Battery

Engine Room J/B

B–W

W–B

V1 VSV (EVAP)

B–R

EFI
Relay

5

2B

4

2F

3

2D

1

2I

1

2

5

3

EFI

W–L

MREL

1

2

7

E8

EVAP1

W–B

1

3

W

W

W

A

J2
J/C

ED

DI–74

–

DIAGNOSTICS

ENGINE

LEXUS RX300   (RM785E)

DTC

P0443

Evaporative Emission Control System Purge
Control Vent Control Malfunction

CIRCUIT DESCRIPTION

To reduce HC emissions, evaporated fuel from the fuel tank is routed through the charcoal canister to the
intake manifold for combustion in the cylinders.
The engine ECU changes the duty signal to the VSV for the EVAP so that the intake quantity of HC emissions
is appropriate for the driving conditions (engine load, engine speed, vehicle speed, etc.) after the engine is
wamed up.

DTC No.

DTC Detecting Condition

Trouble Area

P0443

Proper response to engine ECU command does not occur

S Open or short in VSV circuit for EVAP

S VSV for EVAP

S Engine ECU

WIRING DIAGRAM

DI644–06

A14470

F

E

E

F

VSV is ON

VSV is OFF

Air

Air

–

DIAGNOSTICS

ENGINE

DI–75

LEXUS RX300   (RM785E)

INSPECTION PROCEDURE
Hand–held tester:

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 was warmed up or not, the air–fuel ratio was lean or rich, etc. at the time of the
malfunction.

1

Connect hand–held tester and check operation of VSV for EVAP.

PREPARATION:
(a)

Connect the hand–held tester to the DLC3.

(b)

Turn the ignition switch ON and push the hand–held tes-
ter main switch ON.

(c)

Select the ACTIVE TEST mode on the hand–held tester.

CHECK:
Check the operation of the VSV when the VSV is operated by
the hand–held tester.
OK:

VSV is ON:
Air from port E flows out through port F.
VSV is OFF:
Air from port E is flows out through the air filter.

OK

Check for intermittent problems (See page 
DI–3).

NG

2

Check VSV for EVAP (See page FI–59).

NG

Replace VSV for EVAP.

OK

3

Check for open and short in harness and connector between EFI main relay and
engine ECU (See page IN–32).

NG

Repair or replace harness or connector.

OK