This may be a problem with the EVAP system vent control valve. There are some suggestions that if this valve sticks closed, you will have the problem with refueling as you describe. Mine stuck open venting the tank at all times. Only thing I experienced was a CEL. The valve is behind the drivers side rear wheel. It is attached to the EVAP canister with two 10mm bolts, has one plug on it, and one hose to remove. Take it off and jump it on the battery. It should open and close as you apply the voltage. Some say lubing it up with WD40 can get a stuck one moving again. Mine was too rusted. The part is about $120 at the dealer. There are two styles so make sure you get the right one (no returns cause its electrical).