service engine soon light was on ...took it to autozone and the code number was po455:

description: EVAP large leak detected: explanation: the ecm has detected a large leak in the Evaporative emissions control system

so the guy gave me a brand new fuel cap cuz thats usually the main promblem and he cleared the code but a day later the "check fuel cap" lightcame on

so if its not the fuel cap what else could it be?

 

Maybe he gave you a crap fuel cap, check and make sure it's tight, you can't overtighten it.

 

I've had the same issue for a while now. I've replaced the cap and fiddled with all the lines to the tank.. Not sure what the problem is.