Welcome to the forum. Both your codes lead to the same thing.....
# P0456-EVAP SYSTEM SMALL LEAK
# P0457-EVAP SYSTEM - LOOSE FUEL CAP
The cap has to be turned for at least 3 clicks of the lock when your finished filling up. Once it's on (the check engine light) it might take a day or 3 to go out as the sensor has to check to see if the fault is cleared a number of times.
So, as soon as you (or bilkerchick
) see that fault, get out and turn the cap a few times and then wait a day or so for the light to go out. If it doesn't, you might want to invest in a new cap.
Disconnecting the negative terminal usually clears the code but not on this particular fault.
I deleted your other post as it was a duplicate of this one.