2001 TOYOTA AVALON Service Repair Manual

DI-90
- DIAGNOSTICSENGINE
246 Author
: Date
:
2001 AVALON (RM808U)
Check and replace charcoal canister (See
page IN-30).
OBD II scan tool (excluding TOYOTA hand-held tester):
1 Check whether hose close to fuel tank have been modified, and check whether
there are signs of any accident near fuel tank or charcoal canister (See page
DI-74, step 1).
NG Repair or replace.
OK
2 Check that fuel tank cap is TOYOTA genuine parts (See page DI-74, step 2).
NG Replace to TOYOTA genuine parts.
OK
3 Check that fuel tank cap is correctly installed (See page DI-74, step 3).
NG Correctly install fuel tank cap.
OK
4 Check fuel tank cap (See page EC-6, step 4).
NG Replace fuel tank cap.
OK
5 Check filler neck for damage (See page DI-74, step 5).

- DIAGNOSTICSENGINE
DI-91
247 Author
: Date
:
2001 AVALON (RM808U)
NG Replace filler pipe.
OK
6 Check vacuum hoses between vapor pressure sensor and fuel tank, charcoal
canister and VSV for pressure switching valve, and VSV for pressure switching
valve and charcoal canister (See page DI-74, step 6).
NG Repair or connect VSV or sensor connector.
OK
7 Check hose and tube between fuel tank and charcoal canister (See page
DI-74, step 7).
NG Repair or replace.
OK
8 Check VSV connector for EVAP, VSV connector for CCV, VSV connector for pres-
sure switching valve and vapor pressure sensor connector for looseness and
disconnection.
NG Repair or connect VSV or sensor connector.
OK
9 Check vacuum hoses ((8), (9), (10) and (11) in Fig. 1 in circuit description).
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.

DI-92
- DIAGNOSTICSENGINE
248 Author
: Date
:
2001 AVALON (RM808U)
OK
10 Check voltage between terminals VC and E2 of ECM connector (See page
DI-74, step 9).
NG Check and replace ECM (See page IN-30).
OK
11 Check voltage between terminals PTNK and E2 of ECM connectors (See page
DI-74, step 10).
OK Go to step 13.
NG
12 Check for open and short in harness and connector between vapor pressure sen-
sor
and ECM (See page IN-30).
NG Repair or replace harness or connector.
OK
Replace vapor pressure sensor.

A02028
ON
EVP1
Air
Air
F
F E
E ONOFF
VSV is ON
VSV is OFF
- DIAGNOSTICSENGINE
DI-93
249 Author
: Date
:
2001 AVALON (RM808U)
13 Check VSV for EVAP.
PREPARATION:
(a) Remove the glove compartment (See page SF-82).
(b) Turn the ignition switch ON.
CHECK:
Check the VSV function.
(1) Connect between terminal EVP1 of the ECM con-
nector and body ground (ON).
(2) Disconnect between terminal EVP1 of the ECM
connector and body ground (OFF).
OK:
(1) VSV is ON:
Air from port E flows out through port F.
(2) VSV is OFF:
Air does not flow from port E to port F.
OK Go to step 16.
NG
14 Check operation of VSV for EVAP (See page SF-65).
OK Go to step 15.
NG
Replace VSV and clean vacuum hoses between throttle body and VSV for EVAP, and VSV for
EVAP and charcoal canister, and then check charcoal canister.
15 Check for open and short in harness and connector between EFI main relay
(Marking: EFI) and VSV for EVAP, and VSV for EVAP and ECM (See page
IN-30).
NG Repair or replace harness or connector.

BE6653
A10281A10310
A10951
VSV is ON
VSV is OFF ON
CCV
OFF ON
Air
E Air
E
FF
DI-94
- DIAGNOSTICSENGINE
250 Author
: Date
:
2001 AVALON (RM808U)
OK
Check and replace ECM (See page IN-30).
16 Check VSV for CCV.
PREPARATION:
(a) Remove the grove compartment (See page SF-82).
(b) Turn the ignition switch ON.
CHECK:
Check the VSV function.
(1) Connect between terminal CCV of the ECM con-
nector and body ground (ON).
(2) Disconnect between terminal CCV of the ECM con-
nector and body ground (OFF).
OK:
VSV is ON:
Air does not flow from port E to port F.
VSV is OFF:
Air from port E flows out through port F.
OK Go to step 19.
NG
17 Check operation of VSV for CCV (See page SF-70).
OK Go to step 18.
NG
Replace VSV and charcoal canister, and then
clean vacuum hose between charcoal canis-
ter and VSV for CCV.

BE6653
A10278A10604A10952
VSV is ONVSV is OFF ON
TBP
OFFON
Air
E Air
E
FF
- DIAGNOSTICSENGINE
DI-95
251 Author
: Date
:
2001 AVALON (RM808U)
18 Check for open and short in harness and connector between EFI main relay
(Marking: EFI) and VSV for CCV, and VSV for CCV and ECM (See page IN-30).
NG Repair or replace harness or connector.
OK
Check and replace ECM (See page IN-30).
19 Check VSV for pressure switching valve.
PREPARATION:
(a) Remove the grove compartment (See page SF-82).
(b) Turn the ignition switch ON.
CHECK:
Check the VSV function.
(1) Connect between terminal TBP of the ECM connec-
tor and body ground (ON).
(2) Disconnect between terminal TBP of the ECM con-
nector and body ground (OFF).
OK:
(1) VSV is ON:
Air from port E flows out through port F.
(2) VSV is OFF:
Air does not from flow port E to port F.
OK Go to step 22.
NG
20 Check operation of VSV for pressure switching valve (See page SF-72).
OK Go to step 21.

DI-96
- DIAGNOSTICSENGINE
252 Author
: Date
:
2001 AVALON (RM808U)
NG
Replace VSV and charcoal canister, and then clean vacuum hoses between charcoal canister
and VSV for pressure switching valve, and VSV for pressure switching valve and fuel tank.
21 Check for open and short in harness and connector between EFI main relay
(Marking: EFI) and VSV for pressure switching valve, and VSV for pressure
switching valve and ECM (See page IN-30).
NG Repair or replace harness or connector.
OK
Check and replace ECM (See page IN-30).
22 Check the fuel tank over fill check valve (See page EC-6).
NG Replace fuel tank over fill check valve or fuel
tank.
OK
Check and replace charcoal canister (See
page IN-30).

A10145
ECM
Fuel Tank Charcoal Canister VSV for
EVAPFuel Tank Over
Fill Check Valve
Vapor Pressure Sensor
VSV for
CCVVSV for
Pressure
Switching Valve
- DIAGNOSTICSENGINE
DI-97
253 Author
: Date
:
2001 AVALON (RM808U)
DTC P0450 Evaporative Emission Control System Pres-
sure Sensor Malfunction
DTC P0451 Evaporative Emission Control System Pres-
sure Sensor Range/Performance
CIRCUIT DESCRIPTION
The vapor pressure sensor, VSV for canister closed valve (CCV) and VSV for pressure switching valve are
used to detect abnormalities in the evaporative 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 P0450 or P0451 is recorded by the ECM when the vapor pressure sensor malfunction.
DTC No.DTC Detecting ConditionTrouble Area
P0450
10 seconds or less after engine starting condition vapor pres-
sure sensor fixed value continues for fixed value or more: (2
trip detection logic)
P0451
Vapor pressure sensor output extremely changes under condi-
tions of (a) and (b): (2 trip detection logic)
(a) Vehicle speed: 0 km/h (0mph), Engine speed: Idling and
VSV for pressure switching valve is OFF
(b) vavor pressure sensor value
opening pressure valve of
charcoal canister
Open or short in vapor pressure sensor circuit

Vapor pressure sensor

ECM
DI081-04