Every so often, when I switch to 4wd, the display flashes between 2wd then 4wd, back and forth. The ATV stays in 2wd and the only way I can get it to reset is to disconnect the battery for a few seconds--then I connect it back and everything works OK. Last time this happened I was climbing a rugged rocky trail, and it was a little frightening not to get into 4wd as expected.