Got a used Sportsman 400 4x4 and the 4x4 worked when I first got it, but it sat for a few years, and when I got it going again, the 4x4 doesn't work anymore. When I push the 4x4 button no 4x4 light comes on, and the front wheels never engage. What steps do I take to diagnose the problem? I have a manual but the wiring diagram for my model isn't listed.... just for the 96 500 model. Where do I start?