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P0450 evap system pressure sensor P0446 charcoal canister vent control valve. Vent valve leakage can cause the evap pressure sensor not to see fuel tank pressure when it should. Related codes such as this could cause more fuel Hydrocarbon emissions into the environment. Your alternatives buy used parts and replace them your self 1 to 2 hundred dollars or take your chances. Dealership mechanics or service shops. The dealer can operate the vent valve and purge valve and pressure test the fuel tank systems not may shops have the necessary test equipment to do that. Dealer diagnosis $100 and labor to replace the vent valve approx $50 and cost of the vent valve and o ring. Evap Boost Pressure Sensor is a costly part most likely not necessary until tested bad. Good Luck