Check fuel cap message stays on, although the cap and seal looked fine, I changed it, made sure it was on nice and tight, clicked it slowly, I get no codes, i checked underneath near the canister for bad hoses, the message sometimes dissapears but comes back shortly after. If i bring it to the dealer for scanning, can they even detect it without having a code? What else can I check, can it be one of the solenoids without a code?