Test the wires they should be 12 V and ground when engine on. The valve should be open when the ignition is off so that you can fill the tank; that is why it is hard to fill. Like trying to fill a soda pop bottle with a hose and no vent. If the vent is working properly the charcoal canister is suspect.

 

Moved to a new thread because it is too confusing to hijak 3 year old threads.

 

Some just cut an crimp the pigtail to the original harness if you find a corrosion issue there.

 

P0446 means there is an obstruction in the vent system.

A clogged charcoal filter; the media inside the canister.
A bent/kinked vent tube. From the valve to the top of the filler pipe.
A clogged/stuck valve.
A stuck closed purge valve.
A bent/kinked EVAP return pipe.