TOYOTA PRIUS 2001 Service Repair Manual

± DIAGNOSTICSENGINE
DI±131
2001 PRIUS (RM778U)
DTC P1431Vacuum Sensor for HC Adsorber and Catalyst Sys-
tem Circuit Range/Performance Problem
CIRCUIT DESCRIPTION
Refer to DTC P1430 on page DI±127.
DTC No.DTC Detecting ConditionTrouble Area
P1431
Conditions (a), (b), (c) and (d) continue with more than 10
seconds: (2 trip detection logic)
(b) PIM > 3.96 V
(c) VSV for HC Adsorber and Catalyst System is ON
(d) Engine speed is 1,000 rpm or more
(e) THW
0°C (32°F)

Vacuum sensor for HC adsorber and catalyst systemP1431Conditions (a), (b) and (c) continue with more than 10 se-
cond: (2 trip detection logic)
(a) PIM < 1.2 V
(b) Engine stopped
(c) VSV for HC Adsorber and Catalyst System is OFF
(d) THW
0°C (32°F)

Vacuum sensor for HC adsorber and catalyst system

Vacuum line
INSPECTION PROCEDURE
HINT:

If DTCs P1430, P1431, P0110, P0115, P0116, P0120, 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.

When a bypass valve has a trouble, it is possible that DTC P1341 will be detected ahead of DTC
P1436, and P1437, so in case that P1431 even if they are not memorized.
1 Are there any other codes (besides DTC P1431) being output?
YES Go to relevant DTC chart.
NO
DI7SZ±01

DI±132
± DIAGNOSTICSENGINE
2001 PRIUS (RM778U)
2 Check vacuum sensor for HC adsorber and catalyst system (See page SF±51).
NG Replace vacuum sensor.
OK
Check vacuum line for vacuum sensor for
blockage.

± DIAGNOSTICSENGINE
DI±133
2001 PRIUS (RM778U)
DTC P1436 Bypass Valve Malfunction
CIRCUIT DESCRIPTION
Before the engine is started, the bypass valve remains open. When the engine is cold started, the ECM out-
puts a signal to the VSV (for HC adsorber and catalyst system), which open the passage between the intake
manifold and the actuator, thus applying a vacuum to the actuator. As a result, the bypass valve closes.
Immediately after the engine has started, the exhaust gases pass through the adsorber material in with HC
becomes adsorbed and stored for a certain length of time (until the temperature of the front TWC rises).
Thus, the release of HC into the atmosphere is prevented when the temperature of the TWC is low.
After the TWC has warmed up, the VSV closes the passage between the intake manifold and the actuator,
causing the bypass valve to open. Then, as the temperature of the rear TWC rises, the temperature of the
adsorber material that surrounds it also rises, and the HC starts to desorb, and becomes cleaned by the
TWC.
Furthermore, this system activates the VSV when decelerating and the HC adsorber has become the speci-
fied temperature, allowing the vacuum from the intake manifold to close the bypass valve in order to scav-
enge the HC that remains in the adsorber material.
DTC No.DTC Detecting ConditionTrouble Area
P1436
With cold start when the water temperature and intake air
temperature were ±10 °C (14 °F)to 40 °C (104 °F), and
when the water temperature has reached 45 °C (113 °F) or
more and the engine load factor has become more than 30
%, the valve operation is not preformed normally.

Vacuum line

Actuator

Front exhaust pipe
INSPECTION PROCEDURE
1 Check vacuum hose and tube between VSV and actuator for HC adsorber and
catalyst system.
CHECK:
Check that the vacuum hose and tube for clog and deformation.
NG Repair or replace.
OK
2 Check actuator operation (See page EC±13).
OK Recheck after assembly.
NG
DI7T0±01

DI±134
± DIAGNOSTICSENGINE
2001 PRIUS (RM778U)
3 Check that dirt such as mud is deposited on lever and shaft of bypass valve.
YES Remove dirt and check again.
NO
4 Check that actuator's rod and bracket is deformed.
YES Repair or replace actuator.
NO
5 Check bypass valve operation (See page EC±13).
NG Replace front exhaust pipe.
OK
6 Check actuator operation (See page EC±13).
NG Replace actuator.
OK
Repair or replace front exhaust pipe.

± DIAGNOSTICSENGINE
DI±135
2001 PRIUS (RM778U)
DTC P1437 Vacuum Line Malfunction
CIRCUIT DESCRIPTION
Refer to DTC P1436 on page DI±133.
DTC No.DTC Detecting ConditionTrouble Area
P1437
With cold start when the water temperature and intake air
temperature were ± 10 °C (14 °F) to 40 °C (104 °F), and
when the water temperature has reached 45 °C (113 °F) or
more and the engine load factor has become more than 30
%, the negative pressure has abnormality.
Vacuum line

VSV for HC adsober and catalyst system

Vacuum sensor for HC adsober and catalyst system

Check valve
INSPECTION PROCEDURE
TOYOTA hand±held tester:
1 Check vacuum hoses and tube between intake manifold and actuator.
CHECK:
(a) Check that the vacuum hoses is connected correctly.
(b) Check the vacuum hose for looseness and disconnection.
(c) Check the vacuum hose and tube for cracks, holes and damage.
(d) Check the vacuum hose for clog.
NG Repair or replace.
OK
2 Check for open and short in harness and connector between VSV (for HC adsob-
er and catalyst system) and ECM (See page IN±41).
NG Repair or replace harness or connector.
OK
3 Check VSV (for HC adsorber and catalyst system) (See page SF±47).
NG Replace VSV.
OK
DI7T1±01

DI±136
± DIAGNOSTICSENGINE
2001 PRIUS (RM778U)
4 Check vacuum stored in vacuum hose between check valve and actuator.
PREPARATION:
(a) Disconnect the vacuum hose from the pressure sensor for HC adsober and catalyst system.
(b) Connect the MITYVAC (Hand±held vacuum pump) to the vacuum hose.
(c) Connect the TOYOTA hand±held tester to the DLC3.
CHECK:
(a) VSV (for HC adsober and catalyst system) is operate by TOYOTA hand±held tester.
(b) Apply vacuum of 55 kPa (420 mmHg, 16.24 in.Hg).
(c) Check that the vacuum after 30 sec.
OK:
The vacuum is 25 Kpa (188 mmHg, 7.38 in.Hg) or more.
OK Check and replace vacuum hose between in-
take manifold and actuator.
NG
5 Check check valve.
NG Replace check valve.
OK
6 Check stored vacuum of VSV.
NG Replace VSV (for HC adsober and catalyst sys-
tem).
OK
7 Check stored vacuum of actuator(See page EC±13).
NG Replace actuator.
OK

± DIAGNOSTICSENGINE
DI±137
2001 PRIUS (RM778U)
Check and replace vacuum hose and tube
between check valve and actuator.
OBD II scan tool (excluding TOYOTA hand±held tester):
1 Check vacuum hoses and tube between intake manifold and actuator.
CHECK:
(a) Check that the vacuum hoses is connected correctly.
(b) Check the vacuum hose for looseness and disconnection.
(c) Check the vacuum hose and tube for cracks, holes and damage.
(d) Check the vacuum hose and tube for clog.
NG Repair or replace.
OK
2 Check for open and short in harness and connector between VSV (for HC adsob-
er and catalyst system) and ECM (See page IN±41).
NG Repair or replace harness or connector.
OK
3 Check VSV (for HC adsober and catalyst system) (See page SF±47).
NG Replace VSV.
OK

A14019
ONHCC
DI±138
± DIAGNOSTICSENGINE
2001 PRIUS (RM778U)
4 Check vacuum stored in vacuum hose between check valve and actuator.
PREPARATION:
(a) Remove the ECM with connector still connected (See
page SF±62).
(b) Disconnect the vacuum hose from the vacuum sensor (for
HC adsober and catalyst system).
(c) Connect the MITYVAC (Hand±held vacuum pump) to the
vacuum hose.
CHECK:
(a) Connect the terminal HCC of the ECM and body ground.
(b) Apply a vacuum of 55 kPa (420 mmHg, 16.24 in.Hg).
(c) Check that the vacuum after 30 sec.
OK:
The vacuum is 25 Kpa (188 mmHg, 7.38 in.Hg) or
more.
OK Check and replace vacuum hose between
check valve and actuator.
NG
5 Check check valve.
NG Replace check valve.
OK
6 Check stored vacuum of VSV (See page SF±47).
NG Replace VSV for HC adsober and catalyst sys-
tem.
OK

± DIAGNOSTICSENGINE
DI±139
2001 PRIUS (RM778U)
7 Check stored vacuum of actuator (See page EC±13).
NG Replace actuator.
OK
Check and replace vacuum hose and tube
between check valve and actuator.

F02660
HV ECUECM
SPDO
SPHV O 6
10
E9 H14
± DIAGNOSTICSENGINE
DI±141
2001 PRIUS (RM778U)
DTC P1525 Resolver Vehicle Malfunction
CIRCUIT DESCRIPTION
DTC No.DTC Detecting ConditionTrouble Area
P1525When signals of vehicle speed is not input from the resolver for
16 sec. or more while rurining at a speed of 20 km/h or more
ECM

HV ECU

Wire harness
WIRING DIAGRAM
DI7T3±01