Getting tighten fuel cap warning and gas fumes in car

Purchased a Genuine Honda fuel cap and installed, hooked up a OBD-ii reader and found No codes shown-I think there should have been a code! Possibly the installation of the new cap may have fixed it. A friend with an identical 2013 civic reported the same problem with dash warning to tighten fuel cap and also gas fumes, and repaired same by cleaning the tank fill area and carefully removing and cleaning the cap seal-verifying the internal check valve was good. On my Honda, only time will tell. Thanks for your help, incidentaly, Haynes only goes up to 2010, and not for Civic LX. Thanks again, Steve in 29

Evap canister purge valve....2, 8mm bolts where the air intake and throttle body meet....my friend is a honda mechanic...they are aware if the issue...its a $28 part at autozone....there is a small return hose you have to take off also