We had an issue with our brand new Onan in our 2009 Class C. Ours didn't even have 10 hours on it. My wife fired up the Generator while I was driving. She tried to heat something in the microwave for 1 minute, but the generator quit after 30 seconds or so. Restarted it and it quit again shortly after start up. Then it never fired up.
The error code, which I do not remember, basically translated to "have generator serviced". It turned out to be a fuel pump that the dealer replaced under warranty.
I would contact Cummins and find out what the warranty of the Generator is. It maybe more than 1 year as previously mentioned. They should also be able to help troubleshoot over the phone or email. Or at the very least find the nearest authorized repair facility.
-Michael