Nissan Repair: 08 Pathfinder P0447 code, vent valve, valve replacement

Question
I have an 08 pathfinder with a P0447 code.  I removed the vent valve and cleaned it, re-installed it and I am still getting the code.  Is there a way to actually test the valve, or should I simply replace it?  I had read a previous post where you'd mentioned that overfilling the tank can cause problems with the canister/vent process. I have 2 teenage boys learning to drive who have overfilled the tank.  If so does that also mean I have to replace the canister too?

Answer
Paul,

First, I would make sure the lines are in good order and the clamps are good.  If these are good I would replace the valve.  Let them know to stop putting gas in when it cuts off the first time.  If the valve replacement does not do the trick you will need another canister.