O2 sensors can flip a code if they are on there way to going bad. It will be intermittent, so keep an eye out.
It can't hurt to get a new gas cap as these go anyway.
If you do disconnect the battery, don't forget to locate you radio code before you do it. You will not want to go to the hassle of getting one from the dealer, esp if it is a long holiday weekend.
Good luck!
