How to disable minor leak in evaporative system code?

Its a gen 2 2009 Prius. I bought the car at about 50K miles. It has 100K miles on it now. I commute in it, and put around 18K miles a year on it. When I got the car I did not know about this very elaborate fuel vapor containment system. So the first times I fueled it up, I fueled it until it was right to the top of the filler neck instead of stopping when the fuel pump kicks off. This caused it to set a code for a minor fuel evaporative system minor leak.. I was hoping that whatever part of the system I forced fuel into would eventually dry out and the pesky code would stop setting. But after around 50K miles, it still is setting that code about 100 miles after the DTCs are cleared. Its not a biggie, except that I sure can't reset codes every 100 miles, and the presence of the check engine light it causes could potentially mask something important. I have an idea that the Toyota dealership charges hundreds and hundreds of dollars any time a mechanic touches a Prius---and there is only one dealership I can take it to within 150 miles.....so I need to come up with some solution myself. Is there no way I can fix this myself? If not, some way I can disable some sensor that sets the fault code?

 

Ok...many thanks, I will buy my own charcoal canister and replace myself. Hopefully the parts are available from 3rd party and I won't have to pay ridiculous price from toyota dealer? The actual code being set is P1455, small evaporative system leak. Wow, this looks like a major job to access the fuel tank bladder where the canister is mounted! I studied the PDF referenced, and it is interesting that there is a fuel cutoff valve designed specifically to prevent overfilling! Yet it allowed me to overfill. And also there is a valve to keep liquid fuel out of the evaporative system....guess that didn't work. This is an unbelievably complex system....no doubt EPA mandated; EPA overkill, over-regulation at its finest, cost everyone big bucks, both in higher costs for initial purchase and for repairs down the road!

 

Yea, I already replaced the cap with aftermarket part. Don't think it was genuine Toyoto...it was so long ago, its probably the Stant cap. A leak at the cap sets the same code? If the cap design changed during the 2009 year, then its very possible my aftermarket cap is not really the correct one...but I don't have a clue to determine that I have got the correct one. I lost track of or discarded the original. But I did compare the aftermarket one with the original and saw no difference that might prevent it from sealing.