Lexus ES300 (1997 year). Manual — part 329

S00044

ECM

Vapor Pressure
Sensor

VSV for Vapor
Pressure Sensor

Fuel Tank

Charcoal Canister

VSV
for EVAP

(1)

(2)

(3)

(4)

(5)

fig. 1

(6)

–

DIAGNOSTICS

ENGINE

DI–93

245

1997 LEXUS ES300 (RM511U)

DTC

P0441

Evaporative Emission Control System
Incorrect Purge Flow

DTC

P0446

Evaporative Emission Control System Vent
Control Malfunction

CIRCUIT DESCRIPTION

The vapor pressure sensor and VSV for vapor pressure sensor are used to detect abnormalities in the evap-
orative emission control system.
The ECM decides whether there is an abnormality in the evaporative emission control system based on the
vapor pressure sensor signal.
DTC P0441 and P0446 are recorded by the ECM when evaporative emissions leak from the components
within the dotted line in fig. 1 below, or when there is a malfunction in either the VSV for EVAP, the VSV for
vapor pressure sensor, or in the vapor pressure sensor itself.

DI09W–01

DI–94

–

DIAGNOSTICS

ENGINE

246

1997 LEXUS ES300 (RM511U)

DTC No.

DTC Detecting Condition

Trouble Area

The pressure in the charcoal canister does not drop during

purge control (2 trip detection logic)

P0441

During purge cut–off, the pressure in the charcoal canister is

very low compared with atmospheric pressure

(2 trip detection logic)

Open or short in VSV circuit for EVAP

Open or short in VSV circuit for vapor pressure sensor

When VSV for vapor pressure sensor is OFF, ECM judges that

there is no continuity between vapor pressure sensor and

charcoal canister (2 trip detection logic)

Open or short in vapor pressure sensor circuit

VSV for EVAP

VSV for vapor pressure sensor

Vapor pressure sensor

P0446

When VSV for vapor pressure sensor is ON, ECM judges that

there is no continuity between vapor pressure sensor and fuel

tank (2 trip detection logic)

Vapor pressure sensor

Vacuum hose cracks, holed blocked, damaged or

disconnected ((1), (4), (5) and (6) in fig. 1)

Charcoal canister cracks, holed or damaged

After the purge cut off operates, the pressure in the charcoal

canister is maintained at atmospheric pressure

(2 trip detection logic)

Charcoal canister cracks, holed or damaged

WIRING DIAGRAM

Refer to DTC P0440 on page

DI–87

for the WIRING DIAGRAM.

INSPECTION PROCEDURE

HINT:If DTC P0441, P0446 or P0450 is output after DTC P0440, first troubleshoot DTC P0441, P0446 or
P0450. If no malfunction is detected, troubleshoot DTC P0440 next.

LEXUS hand–held tester

1

Check VSV connector for EVAP, VSV connector for vapor pressure sensor and
vapor pressure sensor connector for looseness and disconnection.

NG

Repair or connect VSV or sensor connector.

OK

2

Check vacuum hose between intake manifold and VSV for EVAP, VSV for EVAP
and charcoal canister, charcoal canister and VSV for vapor pressure

sensor, and

VSV for vapor pressure sensor and vapor pressure sensor.

CHECK:
(a)

Check that the vacuum hose is connected correctly.

(b)

Check the vacuum hose for looseness and disconnection.

(c)

Check the vacuum hose for cracks, hole, damage and blockage.

NG

Repair or replace.

OK

–

DIAGNOSTICS

ENGINE

DI–95

247

1997 LEXUS ES300 (RM511U)

3

Check voltage between terminals VC and E2 of ECM connector
(See page

DI–87

,

IG–1

).

NG

Check and replace ECM (See page

IN–27

).

OK

4

Check voltage between terminals PTNK and E2 of ECM connectors
(See page

DI–87

,

SF–6

).

OK

Go to step 6.

NG

5

Check for open and short in harness and connector between vapor pressure
sensor and ECM (See page

IN–27

).

NG

Repair or replace harness or connector.

OK

Replace vapor pressure sensor.

A00230

VSV is ON

VSV is OFF

S04610

S04609

DI–96

–

DIAGNOSTICS

ENGINE

248

1997 LEXUS ES300 (RM511U)

6

Check purge flow.

PREPARATION:
(a)

Connect the LEXUS hand–held tester to the DLC3.

(b)

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

(c)

Disconnect from the charcoal canister the vacuum hose
to the VSV for EVAP.

(d)

Start the engine.

CHECK:
When the VSV for EVAP is operated by the LEXUS hand–held
tester, check whether the disconnected hose applies suction to
your finger.
OK:

VSV is ON:
Disconnected hose applies suction to your finger.
VSV is OFF:
Disconnected hose applies no suction to your finger.

OK

Go to step 10.

NG

7

Check vacuum hose between intake manifold and VSV for EVAP, and VSV for
EVAP and charcoal canister.

CHECK:
(a)

Check that the vacuum hose is connected correctly.

(b)

Check the vacuum hose for looseness and disconnection.

(c)

Check the vacuum hose for cracks, hole, damage and blockage.

NG

Repair or replace.

OK

8

Check operation of VSV for EVAP (See page

SF–52

).

NG

Replace VSV for EVAP.

OK