Welcome to the forums. Just a guess, but maybe your speed sensor is bad. I noticed that you had another post about shifting problems. Since the ES system needs input from the speed sensor to shift properly, maybe the speed sensor is responsible for both problems. Since the 2001 model doesn't store trouble codes, the only sure way to find the problem is to check each component. A service manual will show you how to check each component.
Most 4-wheeler problems are caused by a loose nut connecting the handlebars and the seat!!
You only need two tools in life -- WD-40 and duct tape. If it doesn't move and should, use the WD-40. If it shouldn't move and does, use the duct tape.