P0446 is a specific EVAP system trouble code, indicating a problem with the EVAP Vent Control Circuit. Your Toyota Camry might have a stuck open, dirty (causing high resistance), or shorted out, EVAP vent valve. The vent valve is used to seal the EVAP canister. More than likely upon repairing (replacing) the EVAP vent valve you will trouble code P0446. The vent valve is part of the Toyota Camry EVAP Charcoal Canister, and must be replaced as one unit.
EVAP Vent Valve Operation:
EVAP vent valve is used to seal the EVAP system (charcoal canister, gas tank, vapor hoses) in order for the ECM to pressurize the EVAP system and ensure there are no leaks. The 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. P0446 can also set when the ECM detects that EVAP system is unable to achieve or maintain vacuum during test.
