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Q: Check engine light due to EVAP P0446 on 2002 Toyota Sienna

Checked everything and replaced gas cap and canister. After couple weeks check engine light turned on and the same code appears
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P0446 Evaporative Emission Control System Vent Control Circuit Malfunction Evap vent valve has only one purpose. It closes in order to seal the vent so the EVAP system can pressurize and ensure there are no leaks. Evap vent valve is usually supplied Batt. voltage with key on. The ECM's driver controls the ground, and when grounded, activates the valve (closing it). If the ECM detects a short to ground, and open,or a short to battery voltage on the control circuit, P0446 will set. Code also may refer to ECM detecting that EVAP system is unable to achieve or maintain vacuum during test.
SymptomsThere will be no obvious symptoms to driver, other than MIL illumination.
CausesA code P0446 could mean one or more of the following has happened:

Faulty vent valve
Open, short or excessive resistance on Vent valve control circuit
Blockage of vent valve

Possible SolutionsWith a P0446 OBD-II trouble code, here are some things to try:

Replace Vent valve
Repair open, short, or resistance problem in control circuit
Repair open, or short, or resistance problem in power circuit
Replace PCM
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