^
In addition to a loose gas cap, there is a strong possibility that the technician who worked on your car failed to properly connect an electrical connector under the hood. Put the burden on the dealership to resolve this problem before you go into panic mode.
While I wouldn’t want a VW Routan (or the mechanically identical Chrysler van), the presence of a lit-up CEL is not sufficient reason to dump a 2 year old vehicle that now has a new engine.