OK So my "service engine soon" light came on. Went to NAPA Auto Parts to have it read. The code said: "EVAP Emission Control System Leak Detected Large".

I was told it was most likely a loose gas cap. I've filled up the tank several times and tightly re-secured the factory gas cap. Still getting the reading.

Any ideas?

 

a 455 code can be a gas cap, but usually it is something more involved like a leak in one of the evap lines.

 

Buy a new gas cap first, just because yours is tight does not mean that it is tight.
$15 and if thats not it then your only out $15, if you take it in they will charge you $100 just to look at it...and then sell you a $15 gas cap for $35.