Toyota Tundra. Manual - part 1627

Fig. 260: EVAP System Diagram
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

While the engine is running, if a predetermined condition (closed-loop, etc.) is met, the purge VSV is opened by
the ECM and stored fuel vapors in the canister are purged into the intake manifold. The ECM changes the duty
cycle ratio of the purge VSV to control purge flow volume.

The purge flow volume is also determined by the intake manifold pressure. Atmospheric pressure is allowed
into the canister through the vent valve to ensure that the purge flow is maintained when the negative pressure
(vacuum) is applied to the canister.

The following two monitors run to confirm the appropriate EVAP system operation.

1. Key-off monitor

This monitor checks for EVAP (Evaporative Emission) system leaks and canister pump module
malfunctions. The monitor starts 5 hours* after the ignition switch is turned off. At least 5 hours are
required for the fuel to cool down to stabilize the EVAP pressure, thus making the EVAP system monitor
more accurate.

The leak detection pump creates negative pressure (vacuum) in the EVAP system and the pressure is
measured. Finally, the ECM monitors for leaks from the EVAP system, and malfunctions in both the
canister pump module and purge VSV, 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.

2. Purge flow monitor

The purge flow monitor consists of 2 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 (Vacuum Switching Valve) 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

NOTE:

In this vehicle's EVAP system, turning ON the vent valve does not seal off the
EVAP system. To check for leaks in the EVAP system, disconnect the air inlet
vent hose and apply pressure from the atmospheric side of the canister.

2009 Toyota Tundra

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

Saturday, June 19, 2010 7:34:47 PM

Page 601

The vent valve is turned ON (closed) and the EVAP pressure is measured. If the variation in the
pressure is less than 0.5 kPa-g (3.75 mmHg-g), the ECM interprets this as the purge VSV being
stuck closed, and illuminates the MIL and sets 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.

Fig. 261: EVAP Purge Flow
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

COMPONENT OPERATION CHART

Component

Operation

Canister

Contains activated charcoal to absorb EVAP (Evaporative Emissions) generated in
fuel tank.

Cut-off valve

Located in fuel tank. Valve floats and closes when fuel tank 100% full.

Purge VSV
(Vacuum
Switching Valve)

Opens or closes line between canister and intake manifold. ECM uses purge VSV to
control EVAP purge flow. In order to discharge EVAP absorbed by canister to intake
manifold, ECM opens purge VSV. EVAP discharge volume to intake manifold
controlled by purge VSV duty cycle ratio (current-carrying time) (Open: ON; Closed:
OFF).

Refueling valve

Controls EVAP pressure from fuel tank to canister. Valve consists of diaphragm,
spring and restrictor (diameter: 0.08 inch). When fuel vapor and pressure inside fuel
tank increase, valve opens. While EVAP purged, valve closes and restrictor prevents
large amount of vacuum from affecting pressure in fuel tank. Valve opened while
refueling.

Roll-over valve

Located in fuel tank. Valve closed by its own weight when vehicle overturns to
prevent fuel from spilling out.

Soak timer

Built into ECM. To ensure accurate EVAP monitor, measures 5 hours (+/-15 min)
after ignition switch turned off. This allows fuel to cool down, stabilizing EVAP
pressure. When approximately 5 hours elapsed, ECM activates (refer to Fig. 264).

Canister pump
module

Consists of (a) to (d) below. Canister pump module cannot be disassembled.

(a) Vent valve

Vents and closes EVAP system. When ECM turns valve ON, EVAP system closed.
When ECM turns valve OFF, EVAP system vented. Negative pressure (vacuum)

2009 Toyota Tundra

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

Saturday, June 19, 2010 7:34:47 PM

Page 602

Fig. 262: Canister Pump Module
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

Fig. 263: Canister Pressure Sensor Specification
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

created in EVAP system to check for EVAP leaks by closing purge VSV, turning on
vent valve (closed) and operating leak detection pump (refer to Fig. 262).

(b) Canister
pressure sensor

Indicates pressure as voltages. ECM supplies regulated 5 V to canister pressure
sensor, and uses feedback from sensor to monitor EVAP system pressure (refer to
Fig. 263).

Creates negative pressure (vacuum) in EVAP system for leak check.

(d) Reference
orifice

Has opening with 0.02 inch diameter. Vacuum produced through orifice by closing
purge VSV, turning off vent valve and operating leak detection pump, to monitor
reference pressure. Reference pressure indicates small leak of EVAP.

2009 Toyota Tundra

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

Saturday, June 19, 2010 7:34:47 PM

Page 603

Fig. 264: Soak Timer Circuit
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

WIRING DIAGRAM

Fig. 265: Canister Pressure Sensor - Wiring Diagram
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

CONFIRMATION DRIVING PATTERN

HINT:

After a repair, check Monitor Status by performing the Key-Off Monitor Confirmation and Purge Flow Monitor
Confirmation described below.

1. KEY-OFF MONITOR CONFIRMATION

2009 Toyota Tundra

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

Saturday, June 19, 2010 7:34:47 PM

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