Onan Generator error code

I have a newer Onan Generator 5500w propane. It has worked flawlessly for 3 years. I also start it from time to time and do routine maintenance. Now it starts runs a few seconds and dies. I get the #36 error code. ( For those not familar with Onans if something is wrong the start stop switch will flash dots and dashes to indicate an error code which you can then refer to in the manual.) In this case it is #36 engine stop fault (engine stopped without command controller) The only solution it lists is to check for propane supply. Which both tanks are full. Any ideas how to proceed from here?
Thanks in advance.
Jim