Code P0446 is in reference to the Vent solenoid.
The charcoal canister should be located near the radiator support, the vent valve is usually near it.
It will have a 2 wire connector, when key is on there will be 12v on 1 wire, the other wire goes to the computer(PCM), the computer grounds that wire to open and close solenoid.
Code P0446 usually means there is a fault in that circuit.
If you give the solenoid 12v and a ground it should "click"
On the larger filler hose for the gas tank there is a smaller vent hose that runs right next to it, this allows air to come out of the tank while you are filling the tank.
At the top off the filler neck you should see were that vent hose connects, on some you can put a small rubber hose on it and blow, to see if it is clear.