Toyota Tundra (2015 year). Manual — part 1673
NOTICE:
In this vehicle's EVAP system, turning ON the vent valve does not seal off the EVAP system. To check for leaks
ECM and stored fuel vapors in the canister are purged into the intake manifold. The ECM changes the duty cycle ratio
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 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
for 100 L (26.4 US gal) Fuel Tank:
3UR-FBE ENGINE CONTROL SYSTEM: SFI SYSTEM: EVAP System...
- The vent valve is turned ON (closed) and the EVAP pressure is measured. If the variation in the
pressure is less than 0.4 kPa-g (3.0 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).
for 144 L (38 US gal) Fuel Tank:
- The vent valve is turned ON (closed) and the EVAP pressure is measured. If the variation in the
pressure is less than 0.15 kPa-g (1.125 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
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).
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. 3).
Canister pump
module
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
3UR-FBE ENGINE CONTROL SYSTEM: SFI SYSTEM: EVAP System...
COMPONENT
OPERATION
detection pump (refer to fig. 1).
(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. 2).
(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.
WIRING DIAGRAM
3UR-FBE ENGINE CONTROL SYSTEM: SFI SYSTEM: EVAP System...
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