Paulie G-
Model year 2015 wiring diagrams are
here.
Winnebago did us no favors when after 2009 it chose not to publish diagram sets that it had published up to that time, such as the "Body, 12V Wiring Diagram" and the "Automotive Wiring Diagram." That said, some of the diagrams from 2009 may apply to newer model years.
Here's a link to the pertinent diagram from a 2009 Vista.
When I had problems with the steps, I found the step manufacturer had a decent set of troubleshooting procedures, along with diagrams. What make and model are your coach's steps?
I ended up replacing the controller, which on my (non-Winnie) coach was under the bottom step. Along the way I cleaned up the two grounds that the step circuits use. Both the controller and the grounds can cause intermittent problems.