2001 TOYOTA PRIUS Service Repair Manual

A14021
HCLSON
A13624
E2 VC ON
(+)
(±)
± DIAGNOSTICSENGINE
DI±129
2001 PRIUS (RM778U)
3 Check voltage between terminals HCLS and E2 of engine ECU connector.
PREPARATION:
(a) Remove the ECM with connector still connected (See
page SF±62).
(b) Turn the ignition switch ON.
CHECK:
Measure the voltage between terminals HCLS and E2 of the
engine ECU connector.
OK:
Voltage: 3.3 ± 3.9 V
OK Check and replace engine ECU
(See page IN±41).
NG
4 Check for open and short in harness and connector between vacuum sensor
and engine ECU.
NG Repair and replace harness or connector.
OK
Replace vacuum sensor (See page SF±50).
When not using hand±held tester:
1 Check voltage between terminals VC and E2 of engine ECU connector.
PREPARATION:
(a) Remove the ECM with connector still connected (See
page SF±62).
(b) Turn the ignition switch ON.
CHECK:
Measure the voltage between terminals VC and E2 of the en-
gine ECU connector.
OK:
Voltage: 4.5 ± 5.5 V
NG Check and replace engine ECU
(See page IN±41).

A14021
HCLSON
DI±130
± DIAGNOSTICSENGINE
2001 PRIUS (RM778U)
OK
2 Check voltage between terminals HCLS and E2 of engine ECU connector.
PREPARATION:
(a) Remove the ECM with connector still connected (See
page SF±62).
(b) Turn the ignition switch ON.
CHECK:
Measure the voltage between terminals HCLS and E2 of the
engine ECU connector.
OK:
Voltage: 3.3 ± 3.9 V
OK Check and replace engine ECU
(See page IN±41).
NG
3 Check for open and short in harness and connector between engine ECU and
vacuum sensor (See page IN±41).
NG Repair or replace harness or connector.
OK
Replace vacuum sensor.

± 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