2001 TOYOTA PRIUS Service Repair Manual

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.

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

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).