Re: check engine light
I had a similar situation a few years ago on my 2002 Chevy chassis. The codes indicated a problem with the emission systems and possibly the fuel system. After more than a few hours of diagnostic shop time at my local Chevrolet dealer they found a corroded wire in the engine compartment. It was probably the connection between the PCM/OBD and the fuel cap/venting hardware at the fuel fill location. There's a chance it was added by Roadtrek when they repositioned the gas tank, but the technician didn't say. That's just my theory and they may not have used GM OEM quality wiring. Again speculation.
Repaired and it's been fine ever since.
Sorry for not adding this sooner but I only just saw this topic.
It's not a sprint(er) (unless you make it one), it's (hopefully) a marathon.
RV - 2018 Navion 24V + 2016 Wrangler JKU