Toyota Tundra 2005 Service - Repair - Maintenance page 1170

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Key−off monitor

This monitor checks for EVAP (Evaporative Emission) system leaks and pump module malfunctions. The

monitor starts 5 hours* after the ignition switch is turned OFF. More than 5 hours are required to allow enough

time for the fuel to cool down to stabilize the Fuel Tank Pressure (FTP), thus making the EVAP system moni-

tor more accurate.

The electric vacuum 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 pump

module and purge VSV, based on the EVAP pressure.

*:If the engine coolant temperature is not below 35_C 5 hours after the ignition switch is turned off, the moni-

tor check starts 2 hours later. If it is still not below 35_C 7 hours after the ignition switch is turned off, the

monitor check starts 2.5 hours later.

Purge flow monitor

The purge flow monitor consists of the two monitors. The 1st monitor is always 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

The vent valve is turned ON (closed) and the EVAP pressure is then measured. If the variation

in the pressure is less than 0.5 kpa (3.75 mmHg), 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.

EVAP Purge Flow:

To Intake Manifold

Fuel tank cap

Pressure Sensor

Vacuum Pump (OFF)

ENGINE (2UZ−FE)

Refueling Valve

0.02 Inch Orifice

To Atmosphere

Vent Valve (OFF)