2001 Pontiac Bonneville gas tank

There is a filler tube that the gas runs through when filling it. Along side of it is a smaller tube that is a vent. When the gas goes into the tank, the air must escape from the vent. Otherwise, it will back up the filler tube and shut the pump. What you need to do is check that vent pipe along the filler tube from under the car. It runs from the top of the filler tube to the tank. Chances are it is damaged, plugged, or partially crushed.

Let me know what you find.
Joe