Most intermittent "Check Engine" alerts on relatively new vehicles are because the gas cap was not tightened enough for the fuel tank to hold pressure. Leaks in filler pipe or vent trigger the same alert, but that would not correct itself and the alert would remain.
I'm surprised on a vehicle that new, you don't have an "information center" or separate light that says "check gas cap" as a distinct notice. Every vehicle I've bought since 2007 has distinguished this alert from the more general one, though in my E-Series it is an information center notice rather than a separate light.
It is true that most RV manufacturers cut the chassis apart to lengthen it, factory wheelbase options just don't cover their needs. They also lengthen at the rear. This, and things that they do connecting chassis to 12V systems in the house, and running lights, tends to cause problems with wiring particularly (sometimes including things that trigger warnings and interfere with chassis systems like ABS and stability assist), but it should be up to the Chevy truck dealer to determine that, even if the RV manufacturer has to pay for the repair.
That only truck dealers service trucks over a certain size (which would include RV chassis) has been the case for at least the past 50 years. The proportion of dealers in metro areas that handle trucks has shrunk as the number of car-only dealers has grown; bailout rules requiring GM to disenfranchise a large number of dealerships hasn't helped.
We don't notice this problem so much in rural areas because where dealerships may be found only in towns 50-200 miles apart, and more than half of their business is commercial, they are almost all truck dealers. Which means that service will be less of a problem when you travel than it is at home.
Almost any auto parts chain or franchise store has a code reader to see if anything is stored in the computer about that "Check Engine." Most will pull the codes for free, while a dealer may charge a minimum "diagnostic" fee, often as much as 30 minutes labor.
Tom Test
Itasca Spirit 29B