2001 TOYOTA PRIUS Service Repair Manual

DI±86
± DIAGNOSTICSENGINE
2001 PRIUS (RM778U)
Replace vapor pressure sensor.
12 Check fuel tank and fuel tank over fill check valve for cracks and damage.
NG Replace fuel tank or fuel tank over fill check
valve.
OK
It is likely that vehicle user did not properly close fuel tank cap. Please explain to customer how
to properly install fuel tank cap.

A14039
ECM
VSV
for EVAP
Charcoal Canister
Fuel Tank Fig. 1
(3) (8)
(9)
(1) (7)
Vapor Pressure
Sensor VSV for
CCV(4)(5)
(6)(2)
Fresh
Air
ValveVSV for Purge Flow
switching Valve
± DIAGNOSTICSENGINE
DI±87
2001 PRIUS (RM778U)
DTC P0441 Evaporative Emission Control System
Incorrect Purge Flow
DTC P0446 Evaporative Emission Control System Vent
Control Malfunction
CIRCUIT DESCRIPTION
The vapor pressure sensor, VSV for canister closed valve (CCV), VSV for purge flow 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.
DTCs P0441 and P0446 are recorded by the ECM when evaporative emissions leak from the components.
1 below, or when there is a malfunction in either the VSV for EVAP, the VSV for purge flow switching valve,
the VSV for CCV or in the vapor pressure sensor itself.
DI7SU±01

DI±88
± DIAGNOSTICSENGINE
2001 PRIUS (RM778U)DTC No.
DTC Detecting ConditionTrouble Area
P0441
Pressure in fuel tank does not drop during purge control (2 trip
detection logic)
P0441During purge cut±off, pressure in fuel tank is very low
compared with atmospheric pressure (2 trip detection logic)
Open or short in vapor pressure sensor circuit

Vapor pressure sensor

Open or short in VSV circuit for EVAPWhen VSV for CCV is ONpressure in fuel tank is maintained
Open or short in VSV circuit for EVAP
VSV f EVAPWhen VSV for CCV is ON, pressure in fuel tank is maintained
hi (2id i l i)
VSV for EVAPat atmospheric pressure (2 trip detection logic)
Open or short in VSV circuit for purge flow switching valve
P0446
Turning the VSV for purge flow switching valve is ON does not
lower the pressure sensor output.

Oen or short in VSV circuit for urge flow switching valve

VSV for purge flow switching valve

Charcoal canister cracked, hole or damaged
P0446Although the VSV for purge flow switching valve is OFF, fluc-
tuation in the pressure sensor output is great.
Open or short in VSV circuit for CCV

VSV for CCV

ECMTurning the VSV for CCV OFF does not charge the pressure
sensor output.
ECM
WIRING DIAGRAM
Refer to DTC P0440 on page DI±81.
INSPECTION PROCEDURE
HINT:

If DTC P0441, P0446, P0450 or P0451 is output after DTC P0440,first troubleshoot DTC P0441,
P0446, P0450 or P0451. If no malfunction is detected, troubleshoot DTC P0440 next.

Read freeze frame data using TOYOTA hand±held tester or OBD II scan tool. Because freeze frame
records the engine conditions when the malfunction is detected. When troubleshooting, it is useful for
determining whether the vehicle was running or stopped, the engine was warmed up or not, the air±fuel
ratio was lean or rich, etc. at the time of the malfunction.

When the ENGINE RUN TIME in the freeze frame data is less than 200 seconds, carefully check the
VSV for EVAP, charcoal canister and vapor pressure sensor.
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±81).
NG Repair or replace.
OK
2 Check that fuel tank cap is TOYOTA genuine parts.
NG Replace to TOYOTA genuine parts.
OK

± DIAGNOSTICSENGINE
DI±89
2001 PRIUS (RM778U)
3 Check that fuel tank cap is correctly installed.
NG Correctly install fuel tank cap.
OK
4 Check fuel tank cap (See page EC±7).
NG Replace fuel tank cap.
OK
5 Check filler neck for damage.
NG Replace filler pipe.
OK
6 Check vacuum hoses ((1), (2) and (3) in Fig. 1 in circuit description.
NG Repair or connect VSV or sensor connector.
OK
7 Check hose and tube around fuel tank and charcoal canister (See page
DI±81).
NG Repair or replace.
OK

DI±90
± DIAGNOSTICSENGINE
2001 PRIUS (RM778U)
8 Check VSV connector for EVAP, VSV connector for CCV, VSV connector for
purge flow switching valve and vapor pressure sensor connector for looseness
and disconnection.
NG Repair or connect VSV or sensor connector.
OK
9 Check vacuum hoses ((4), (5), (6) and (7) 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.
OK
10 Check voltage between terminals VC and E2 of ECM connector (See page
DI±81).
NG Check and replace ECM (See page IN±41).
OK
11 Check voltage between terminals PTNK and E2 of ECM connectors (See page
DI±81).
OK Go to step 13.
NG

A14044
To Throttle Body
± DIAGNOSTICSENGINE
DI±91
2001 PRIUS (RM778U)
12 Check for open and short in harness and connector between vapor pressure
sensor and ECM (See page IN±41).
NG Repair or replace harness or connector.
OK
Replace vapor pressure sensor.
13 Check purge flow.
PREPARATION:
(a) Connect the TOYOTA hand±held tester to the DLC3.
(b) Select the ACTIVE TEST mode on the TOYOTA hand±
held tester.
(c) Disconnect the vacuum hose from the VSV for the EVAP
from the charcoal canister.
(d) Start the engine.
CHECK:
When the VSV for the EVAP is operated by the TOYOTA hand±
held tester, check whether the disconnected hose applies suc-
tion 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 16.
NG