Pretty sure it's supposed to say gas, not bass. I have the same code on my 02, just constantly though not from filling up. Gas cap didn't fix mine and I haven't taken the time to dig further. Check your charcoal canister behind the RH rear wheel, look for cracks etc. Check the wires for damage as they are very pronedue to location. I think mine is either a sensing line or the emissions solenoid (unsure of the proper naming at the moment). Yours sounds more pressure related or something. Could be the filler tube maybe.
Check NASIOC, google the code. I know there is at least one very detailed write up on there.