As someone said, Onan generators are kind of "Chatty" when it comes to telling you how to feel.. Download the owner's manual and look up "Trouble Codes" for more on that.
Several sensors are disabled when starting, enabled when you take your finger off the button.. These include over temp, oil level, and 120vac out sensors.
I'm sure there are others as well but do not know what they are.
The blink code will tell you much, but it can be cryptic. For example "Low battery or Low cranking speed" You know that's not true cause it started after all.. Means no 120vac out.