[BlindHandyMan] check engine gas cap

[Lenny McHugh]

Ok you car guys. My daughter has a 2000 Camry and we have a 2003 grand 
caravan both have the same problem. After filling the gas tank the check 
engine light comes on and the code indicates that it is the gas cap. I 
replaced the caps and it did not fix the problem. The local mechanic told us 
that it is a dealer only fix. I suspect that it is a sensor somewhere. What 
sensor would do this and can it be replaced without going to the dealer?
Lenny