2001 TOYOTA PRIUS O2 sensor

± DIAGNOSTICSENGINE
DI±97
2001 PRIUS (RM778U)
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 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
7 Check vacuum hoses ((1), (2) , (3), (4), (5), (6), (7), (8) and (9) 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

DI±98
± DIAGNOSTICSENGINE
2001 PRIUS (RM778U)
8 Check voltage between terminals VC and E2 of ECM connector (See page
DI±81).
NG Check and replace ECM (See page IN±41).
OK
9 Check voltage between terminals PTNK and E2 of ECM connectors (See page
DI±81).
OK Go to step 11.
NG
10 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.

± 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.

A00022
From
Speed Sensor4±Pulse4±Pulse
Combination
MeterECM ABS ECU
A14030
C10
Combination
Meter
2A7
V±W Instrument Panel J/B
6
2B J27G
V±W5
E10ECM
SPD J28G
B
LJ/C
± DIAGNOSTICSENGINE
DI±105
2001 PRIUS (RM778U)
DTC P0500 Vehicle Speed Sensor Malfunction
CIRCUIT DESCRIPTION
The speed sensor for ABS detects the wheel speed and sends the appropriate signals to the ABS ECU.
The ECU converts these signals into a 4±pulse signal and output it to the combination meter.
After this signal is converted into a more precise rectangular waveform by the waveform shaping circuit in-
side the combination meter, it is then transmitted to the ECM. The determines the vehicle speed based on
the frequency of these pulse signals.
DTC No.DTC Detecting ConditionTrouble Area
P0500
During vehicle is being driven, no vehicle speed sensor signal
to ECM
(2 trip detection logic)

Combination meter

ABS ECU

Open or short in vehicle speed sensor circuit

Vehicle speed sensor

ECM
WIRING DIAGRAM
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 warmed up or not, the air±fuel ratio lean or rich, etc.
at the time of the malfunction.
DI6VG±02

A14031
Throttle Control Motor
with Magnetic ClutchECM
(Shielded)
8
E7M+
7
E7M±
30
E7GE01 L
P 2
1 DI±108
± DIAGNOSTICSENGINE
2001 PRIUS (RM778U)
DTC P1125 Throttle Control Motor Circuit 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 to the throttle valve
opening 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
Conditions (a) and (b) continue for 0.5 seconds:
(a) Throttle control motor output duty
80 %
(b) Throttle control motor current < 0.5 A

Open or short in throttle control motor circuit
P1125Throttle control motor current
16 A
Throttle control motor

ECMCondition (a) continues for 0.6 seconds:
(a) Throttle control motor current
7 A
ECM
WIRING DIAGRAM
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.
DI7SW±01

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

A14056
V1
Vacuum SensorECM
3
BR 2
1V±W Y±R
E9
E82
14
18VC
HCLS
E2 E8 Y±RJ/C
C
J8 B
J9
V±W9
I01
± DIAGNOSTICSENGINE
DI±127
2001 PRIUS (RM778U)
DTC P1430 Vacuum Sensor for HC Adsorber and Cata-
lyst System Circuit Malfunction
CIRCUIT DESCRIPTION
DTC No.DTC Detecting ConditionTrouble Area
P1430Open or short in vacuum sensor circuit

Open or short in vacuum sensor circuit

Vacuum sensor for HC adsorber and catalyst system

ECM
HINT:
After confirming DTC P1430, use the hand±held tester to confirm the manifold absolute pressure from the
CURRENT DATA.
Manifold Absolute Pressure (kPa)Malfunction
Approx. 0
HCLS circuit short
130 or more

VC circuit open or short

HCLS circuit open

E2 circuit open
WIRING DIAGRAM
INSPECTION PROCEDURE
HINT:

If DTCs P1430,P1431, P0110, P0115, P0120 and P0121 are output simultaneously, E2 (sensor
ground) may be open.

Read freeze frame data using hand±held tester. 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.
DI7SY±01