Lexus ES300 (1997 year). Manual — part 327

FI6514

OX Signal Waveform (Oscilloscope)

1.0V

0V

200 m sec./Division

–

DIAGNOSTICS

ENGINE

DI–85

237

1997 LEXUS ES300 (RM511U)

(1) Connect the LEXUS hand–held tester to the DLC3, or connect the probe of the oscilloscope between
terminals OXR, OXL, OXS and E1 of ECM.
(2) Start engine and warm it up with all accessories switched OFF until water temp. is stable.
(3) Race the engine at 2,500

∼

3,000 rpm for about 3 min.

(4) After confirming that the waveform of the heated oxygen sensor, bank 1, 2 sensor 1 (OXR, OXL), oscillate
around 0.5 V during feedback to the ECM, check the waveform of the heated oxygen sensor, bank 1
sensor 2 (OXS).

HINT:If there is a malfunction in the system, the waveform of the
heated oxygen sensor, bank 1 sensor 2 (OXS), is almost the
same as that of the heated oxygen sensor, bank 1, 2 sensor 1
(OXR, OXL), on the left.
There are some cases where, even though a malfunction
exists, the MIL may either light up or not light up.

INSPECTION PROCEDURE

1

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

YES

Go to relevant DTC chart.

NO

2

Check heated oxygen sensor (bank 1, 2 sensor 1) (See page ).

NG

Repair or replace.

OK

DI–86

–

DIAGNOSTICS

ENGINE

238

1997 LEXUS ES300 (RM511U)

3

Check heated oxygen sensor (bank 1 sensor 2) (See page

SF–63

).

NG

Repair or replace.

OK

Replace three–way catalytic converter.

S00043

ECM

Vapor Pressure
Sensor

VSV for Vapor

Pressure Sensor

VSV
for EVAP

Charcoal Canister

Fuel Tank

(1)

(2)

(3)

fig. 1

–

DIAGNOSTICS

ENGINE

DI–87

239

1997 LEXUS ES300 (RM511U)

DTC

P0440

Evaporative Emission Control System
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 P0440 is recorded by the ECM when evaporative emissions leak from the components within the dotted
line in fig. 1 below, or when the vapor pressure sensor malfunctions.

DTC No.

DTC Detecting Condition

Trouble Area

P0440

The fuel tank pressure is atmospheric pressure after the

vehicle is driven for 20 min. (2 trip detection logic)

Vapor pressure sensor

Fuel tank cap incorrectly installed

Fuel tank cap cracked or damaged

Vacuum hose cracked, holed, blocked, damaged or

disconnected ((1) or (2) in fig. 1)

Hose or tube cracked, holed, damaged or loose seal

((3) in fig. 1)

Fuel tank cracked, holed or damaged

Charcoal canister cracked, holed or damaged

DI09V–01

S05717

Vaper Pressure Sensor

From
Ignition Switch

From FL MAIN

J/B

Junction
Connector

EFI

2A

2K

2J

2F

1

7

5

1

3

2

2

4

B–Y

B–Y

J28

J29

B

B

W–B

EC

IK3

9

B–Y

J23
Junction
Connector

B–Y

B–Y

VSV for EVAP

LG

A

A

A

2

1

W–R

VSV for Vapor

2

1

E9

E8

E9

E8

E8

1

13

22

2

8

ECM

5V

VC

PTNK

E1

E2

EVAP1

E01

E01

TPC

Y

L–R

BR

3

2

1

Pressure Sensor

EngineRoom

EFI Relay

DI–88

–

DIAGNOSTICS

ENGINE

240

1997 LEXUS ES300 (RM511U)

WIRING DIAGRAM

INSPECTION PROCEDURE

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.

Ask the customer whether, after the MIL came on, the customer found the fuel tank cap loose and tight-
ened it. Also ask the customer whether the fuel tank cap was loose when refuelling. If the fuel tank cap
was not loose, it was the cause of the DTC. If the fuel tank cap was not loose or if the customer was
not sure if it was loose, troubleshoot according to the following procedure.