Vacuum Leak

Too many possibilities, need tighter info, what code did they get? Could be simple as a bad gasket on your gas cap, system checks itself for leaks. Get the code number, there's info on here to direct you.

Has to do with your evap system, which consists of various hoses, solenoids, gas tank, canister and of course the gas cap. Listed as a small evaporative system leak in the book. First thing I would do is carefully check the gas cap, make sure the gasket is not torn or threads are not crossed, then check the filler pipe along it's length to make sure it's not damaged. Check all hoses for disconnection, breaks, unhooked electrical connectors on the related electrical parts, may take some work on your part to follow the pieces as they wind around the engine, hopefully it's something you can see, if not there are tests that can be run, most are beyond the driveway mechanic's ability as the dealer uses a specialized evap system tester to find problems that aren't readily apparent