Toyota Tundra. Manual — part 1573

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
(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*

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

After second reference pressure measurement, leak check
performed by comparing first and second reference pressure.
If stabilized system pressure higher than second reference

60

seconds

2009 Toyota Tundra

2009 ENGINE PERFORMANCE Engine Control System (3UR-FBE) - Tundra

Fig. 171: Evaporative Emission System Operation Diagram
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

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
stores the DTC (2 trip detection logic).

measurement

pressure, ECM determines that EVAP system leaking.

-

Final check

Atmospheric pressure measured and then monitoring result
recorded by ECM.

-

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

2009 Toyota Tundra

2009 ENGINE PERFORMANCE Engine Control System (3UR-FBE) - Tundra

Fig. 172: EVAP Pressure Chart - Purge Stuck Open
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

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 stores the
DTC (2 trip detection logic).

Fig. 173: EVAP Pressure Chart - Purge VSV Stuck Closed
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

2. PURGE FLOW MONITOR

Fig. 174: EVAP Pressure Chart - Purge Flow Monitor
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

2009 Toyota Tundra

2009 ENGINE PERFORMANCE Engine Control System (3UR-FBE) - Tundra

The purge flow monitor consists of two monitors. The 1st monitor is conducted every time and the 2nd
monitor is activated if necessary.



The 1st monitor

While the engine is running and the purge VSV is ON (open), the ECM monitors the purge flow by
measuring the EVAP pressure change. If negative pressure is not created, the ECM begins the 2nd
monitor.



The 2nd monitor

The vent valve is turned ON (closed) and the EVAP pressure is then measured. If the variation in
the pressure is less than 0.4 kPa-g (3 mmHg-g), the ECM interprets this as the purge VSV being
stuck closed, and illuminates the MIL and stores DTC P0441 (2 trip detection logic).

Atmospheric pressure check:

In order to ensure reliable malfunction detection, the variation between the atmospheric pressures, before and
after conduction of the purge flow monitor, is measured by the ECM.

OBD II MONITOR SPECIFICATIONS

1. Key-off Monitor

Monitor Strategy

MONITOR STRATEGY

Typical Enabling Condition

TYPICAL ENABLING CONDITION

Required Sensors/Components Purge VSV and canister pump module
Frequency of Operation

Once per driving cycle

Duration

Within 15 minutes (varies with fuel in tank)

MIL Operation

2 driving cycles

Sequence of Operation

None

Monitor runs whenever following DTCs not present

P0452, P0453 (EVAP System)

EVAP key-off monitor runs when all of following conditions met -
Atmospheric pressure

70 to 110 kPa-a (525 to 825 mmHg-a)

Battery voltage

10.5 V or more

Vehicle speed

Below 4 km/h (2.5 mph)

Ignition switch

off

Time after key off

5 or 7 or 9.5 hours

Purge VSV

Not operated by scan tool

Vent valve

Not operated by scan tool

2009 Toyota Tundra

2009 ENGINE PERFORMANCE Engine Control System (3UR-FBE) - Tundra