This code will set if you run the motor while putting gas in the tank; or while the gas cap is off. It will also set if you do not tighten the gas cap at least 4 clicks beyond the point where it stops. If one of the above conditions caused the code to set; have the code cleared with a code scanner. It probably will not come back.
The seal on the gas cap can go bad as it ages. If there is a leak at the gas cap seal; the gas cap may need replacing. The code must be cleared with a code scanner after the cause of the problem is fixed.