Toyota Tundra. Manual — part 1259

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. 231).

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)
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. 229).

(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. 230).

(c) Leak detection
pump

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.

2008 Toyota Tundra

2008 ENGINE PERFORMANCE Engine Control System (1GR-FE) - Tundra

Fig. 229: Canister Pump Module Diagram

Fig. 230: Canister Pressure Sensor Output Voltage Graph

2008 Toyota Tundra

2008 ENGINE PERFORMANCE Engine Control System (1GR-FE) - Tundra

Fig. 231: EVAP System - Circuit Diagram

WIRING DIAGRAM

2008 Toyota Tundra

2008 ENGINE PERFORMANCE Engine Control System (1GR-FE) - Tundra

Fig. 232: EVAP System - Wiring Diagram

INSPECTION PROCEDURE

HINT:



Using Techstream monitor results enables the EVAP (Evaporative Emission) system to be confirmed.



Read freeze frame data using the Techstream. Freeze frame data records the engine condition when
malfunctions are detected. When troubleshooting, freeze frame data can help determine if the vehicle was
moving or stationary, if the engine was warmed up or not, if the air-fuel ratio was lean or rich, and other
data from the time the malfunction occurred.

1. CONFIRM DTC

NOTE:

The Techstream is required to conduct the following diagnostic troubleshooting
procedure.

2008 Toyota Tundra

2008 ENGINE PERFORMANCE Engine Control System (1GR-FE) - Tundra