Update -- finally ventured out into the cold, cold shop to peel off the pumpkin's seat & plastic. Upon removing the seat I saw two red/yellow wires dangling as though they may have been connected together.. on closer inspection it looks like they were plugged into a white connector, and worked loose. A few inches away from the now loose end, there is a fuse holder (fuse OK).
I can't find the exact yellow/red wire in my diagram, though. Did KTM ever publish a color wiring diagram for the LC4 640 models? I cannot find a fuse holder with yellow/red wire on my diagram.