2001 TOYOTA PRIUS check engine

A14048BE6653
A14464A14049
FG ON
AirAir
E
EVSV is ON
VSV is OFFVSV is OFF
VSV is ON
TBP
± DIAGNOSTICSENGINE
DI±101
2001 PRIUS (RM778U)
OK
Check and replace ECM (See page IN±41).
17 Check VSV for purge flow switching valve.
PREPARATION:
(a) Remove the ECM with connector still connected (See
page SF±62).
(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 pipe E is flowing out through pipe F.
(2) VSV is OFF:
Air from pipe E flows out through pipe G.
OK Check and replace charcoal canister (See page
EC±7).
NG
18 Check operation of VSV for purge flow switching valve (See page SF±45).
OK Go to step 19.
NG
Replace VSV and charcoal canister, and then clean vacuum hoses ((!), (2) and (3) in Fig. 1 in cir-
cuit description).

DI±102
± DIAGNOSTICSENGINE
2001 PRIUS (RM778U)
19 Check for open and short in harness and connector between EFI main relay
(Marking: EFI) and VSV for purge flow switching valve, and VSV for purge flow
switching valve and ECM (See page IN±41).
NG Repair or replace harness or connector.
OK
Check and replace ECM (See page IN±41).

± DIAGNOSTICSENGINE
DI±103
2001 PRIUS (RM778U)
DTC P0450 Evaporative Emission Control System
Pressure Sensor Malfunction
DTC P0451 Evaporative Emission Control System
Pressure 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 (a) or (b)
continues for 7 seconds or more: (2 trip detection logic)
(a) Vapor pressure sensor value < ±4.0 kPa (±30 mmHg, ±1.2
in.Hg)
(b) Vapor pressure sensor value
2.0 kPa (15 mmHg, 0.6
in.Hg)

Open or short in vapor pressure sensor circuit

Vapor pressure sensor
ECM
P0451
Vapor pressure sensor output extremely changes under condi-
tion:
Vehicle speed: 0 km/h (0mph),Engine speed: Idling (2 trip
detection logic)
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 trouble shoot 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.
DI7SV±01

DI±104
± DIAGNOSTICSENGINE
2001 PRIUS (RM778U)
1 Check voltage between terminals VC and E2 of ECM connector (See page
DI±81).
NG Check and replace ECM (See page IN±41).
OK
2 Check voltage between terminals PTNK and E2 of ECM connectors (See page
DI±81).
OK Check and replace ECM (See page IN±41).
NG
3 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.

A14009
ON
SPD
(+) (±)
AT7809
4.5 ~ 5.5 V
0
DI±106
± DIAGNOSTICSENGINE
2001 PRIUS (RM778U)
1 Check operation of speedometer.
CHECK:
Drive the vehicle and check if the operation of the speedmeter in the combination meter is normal.
HINT:
The ABS ECU is operating normally if the speedometer display is normal.
NG Check and replace combination meter (See
page BE±2) and ABS ECU (See page
IN±41).
OK
2 Check voltage between terminal SPD of ECM connector and body ground.
PREPARATION:
(a) Remove the ECM with connector still connected (See
page SF±62).
(b) Drive the vehicle.
CHECK:
Measure voltage between terminal SPD of ECM connector and
body ground when the wheel is turned slowly.
OK:
Voltage is generated intermittently.
NG Check and repair harness and connector
between combination meter and ECM.
OK
Check and replace ECM (See page IN±41).

A03403A03404A03675
M+ Signal Waveform
5 V/
Division
GND
1 msec./Division
M± Signal Waveform
GND
5 V/
Division
1 msec./Division
± DIAGNOSTICSENGINE
DI±109
2001 PRIUS (RM778U)
1 Check throttle control motor circuit.
PREPARATION:
(a) Connect the oscilloscope between terminals M+ or M±
and E1 of the ECM connectors.
(b) Start the engine.
CHECK:
Check the waveform between terminals M+ or M± and E1 of the
ECM connectors when the engine is idling.
OK:
The correct waveforms are as shown.
HINT:
The waveform frequency varies depending on the throttle
opening.
OK Check and replace ECM (See page IN±41).
NG
2 Check throttle control motor (See page SF±24).
NG Replace throttle control motor with magnetic
clutch (See page SF±29).
OK
3 Check for open and short in harness and connector between throttle control mo-
tor and ECM (See page IN±41).
NG Repair or replace harness or connector.
OK
Check and replace ECM (See page IN±41).

A13630THRO FuseR/B No.2
A13631
BM
(+)(±)
± DIAGNOSTICSENGINE
DI±111
2001 PRIUS (RM778U)
1 Check THRO fuse of R/B No.2.
PREPARATION:
Remove the THRO fuse from the Engine room J/B.
CHECK:
Check the countinuity of the THRO fuse.
OK:
Continuity
NG Check for short in all harness and components
connected to THRO fuse.
OK
2 Check voltage between terminal +BM of ECM connector and body ground.
PREPARATION:
Remove the ECM with connector still connected (See page
SF±62).
CHECK:
Measure the voltage between terminal BM of the ECM connec-
tor and body ground.
OK:
Voltage: 9 ± 14 V
OK Check and replace ECM (See page IN±41).
NG
Check and repair harness or connector be-
tween battery and ETCS fuse, and ETCS fuse
and ECM (See page IN±41).

DI±112
± DIAGNOSTICSENGINE
2001 PRIUS (RM778U)
DTC P1128 Throttle Control Motor Lock Malfunction
CIRCUIT DESCRIPTION
Throttle motor is operated by the ECM and it opens and closes the throttle valve.
The opening angle of the throttle valve is detected by the throttle position sensor which is mounted on the
throttle body and it provides feedback to the ECM to control the throttle motor in order the throttle valve open-
ing angle properly in response to driving condition.
If this DTC is stored, the ECM shuts down the power for the throttle motor, and the throttle valve is fully closed
by the return spring.
DTC No.DTC Detecting ConditionTrouble Area
P1128Lock throttle control motor during control throttle control motor
Throttle control motor

Throttle body
WIRING DIAGRAM
Refer to DTC P1125 on page DI±108.
INSPECTION PROCEDURE
HINT:
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.
1 Check throttle control motor (See page DI±108).
NG Replace throttle control motor
(See page SF±29).
OK
2 Visually check throttle valve.
PREPARATION:
Remove the intake air resonator.
CHECK:
Check whether or not a foreign body is caught between the throttle valve and housing.
NG Remove foreign body and clean throttle body.
DI7SX±01