I have a 2008 John Deere 4720. While brush hogging a field the other day with a few small 1-2 inch diameter trees, the display started saying "Error Code 06". The operators manual says the problem source is "No signal at MFWD speed input". I suspect something just got disconnected or pulled loose from one of those small trees dragging over it.

I've looked over the the electrical connections that I can see and nothing seems disconnected. Does anyone have any ideas of what I should look for or where the "MFWD speed input" is since that's what the manual said the problem was?