Toyota Tundra. Manual — part 1385

DESCRIPTION

The description can be found in the EVAP (Evaporative Emission) System. (See DESCRIPTION ).

INSPECTION PROCEDURE

Refer to the EVAP SYSTEM .

MONITOR DESCRIPTION

The two monitors, Key-Off and Purge Flow, are used to detect malfunctions relating to DTC P0441. The Key-
Off monitor is initiated by the ECM internal timer, known as the soak timer, 5 hours* after the ignition switch is
turned off. The purge flow monitor runs while the engine is running.

1. KEY-OFF MONITOR

5 hours* after the ignition switch is turned off, the leak detection pump creates negative pressure

P0441

Valve) stuck
open

pressure higher than [second
reference pressure x 0.2], ECM
determines that purge VSV stuck
open.



Canister pump
module



Leakage from
EVAP system

switch off

Purge VSV
stuck closed

After EVAP leak check performed,
purge VSV turned ON (open), and
atmospheric air introduced into
EVAP system. Reference pressure
measured at start and at end of
check. If pressure does not return to
near atmospheric pressure, ECM
determines that purge VSV stuck
closed.



Purge VSV



Connector/wire
harness (Purge
VSV - ECM)



ECM



Canister pump
module



Leakage from
EVAP system

While
ignition
switch off

2 trip

Purge flow

While engine running, following
conditions successively met:



Negative pressure not created
in EVAP system when purge
VSV turned ON (open)



EVAP system pressure
change less than 0.5 kPa-g
(3.75 mmHg-g) when vent
valve turned ON (closed)



Atmospheric pressure change
before and after purge flow
monitor less than 0.1 kPa-g
(0.75 mmHg-g)



Purge VSV



Connector/wire
harness (Purge
VSV - ECM)



Leakage from
EVAP line (Purge
VSV - Intake
manifold)



ECM

While
engine
running

2 trip

2008 Toyota Tundra

2008 ENGINE PERFORMANCE Engine Control System (2UZ-FE) - Tundra

(vacuum) in the EVAP system. The ECM monitors for leaks and actuator malfunctions based on the
EVAP pressure.

HINT:

*: If the engine coolant temperature is not below 35°C (95°F) 5 hours after the ignition switch is turned
off, the monitor check starts 2 hours later. If it is still not below 35°C (95°F) 7 hours after the ignition
switch is turned off, the monitor check starts 2.5 hours later.

MONITOR DESCRIPTION

Sequence

Operation

Description

Duration

-

ECM activation

Activated by soak timer 5, 7 or 9.5 hours after ignition switch
turned off.

-

A

Atmospheric
pressure
measurement

Vent valve turned OFF (vent) and EVAP system pressure
measured by ECM in order to register atmospheric pressure.
If pressure in EVAP system not between 70 kPa-a and 110
kPa-a (525 mmHg-a and 825 mmHg-a), ECM cancels EVAP
system monitor.

10

seconds

B

First reference
pressure
measurement

In order to determine reference pressure, leak detection pump
creates negative pressure (vacuum) through reference orifice
and then ECM checks if leak detection pump and vent valve
operate normally.

60

seconds

C

EVAP system
pressure
measurement

Vent valve turned ON (closed) to shut EVAP system.
Negative pressure (vacuum) created in EVAP system, and
EVAP system pressure then measured.
Write down measured value as it will be used in leak check.
If EVAP pressure does not stabilize within 15 minutes, ECM
cancels EVAP system monitor.

15

minutes

(1)

D

Purge VSV monitor

Purge VSV opened and then EVAP system pressure measured
by ECM. Large increase indicates normality.

10

seconds

E

Second reference
pressure
measurement

After second reference pressure measurement, leak check
performed by comparing first and second reference pressure.
If stabilized system pressure higher than second reference
pressure, ECM determines that EVAP system leaking.

60

seconds

-

Final check

Atmospheric pressure measured and then monitoring result
recorded by ECM.

-

(1)

If only a small amount of fuel is in the fuel tank, it takes longer for the EVAP pressure to stabilize.

2008 Toyota Tundra

2008 ENGINE PERFORMANCE Engine Control System (2UZ-FE) - Tundra

Fig. 154: Evaporative Emission Control System Operation Diagram

a. Purge VSV stuck open

In operation C, the leak detection pump creates negative pressure (vacuum) in the EVAP system.
The EVAP system pressure is then measured by the ECM using the canister pressure sensor. If the
stabilized system pressure is higher than [second reference pressure x 0.2], the ECM interprets this
as the purge VSV (Vacuum Switching Valve) being stuck open. The ECM illuminates the MIL and
sets the DTC (2 trip detection logic).

2008 Toyota Tundra

2008 ENGINE PERFORMANCE Engine Control System (2UZ-FE) - Tundra

Fig. 155: EVAP Pressure Graph - Purge VSV Stuck Open

b. Purge VSV stuck closed

In operation D, the canister pressure sensor measures the EVAP system pressure. The pressure
measurement for the purge VSV monitor is begun when the purge VSV is turned ON (open) after
the EVAP leak check. When the measured pressure indicates an increase of 0.3 kPa-g (2.25 mmHg-
g) or more, the purge VSV is functioning normally. If the pressure does not increase, the ECM
interprets this as the purge VSV being stuck closed. The ECM illuminates the MIL and sets the
DTC (2 trip detection logic).

2008 Toyota Tundra

2008 ENGINE PERFORMANCE Engine Control System (2UZ-FE) - Tundra