My Grandson is on the Autisium spectrim. When he was between 1 and 4 he used to bite when ever he was upset. My grandson had delayed speech and could not express his anger and frustration in words. When he would bite he would lose a privilege, like tv or video games or a snack. It took a long time to get him to stop biting. Between the speech therapy, which enabled him to verbally communicate his feelings, and the punishment for biting he stopped. Now he is 6 and when he gets angry he will yell at the person. He gets his point across without needing to do physical harm. Maybe the part that bites isn't able to use speech. Maybe ask this part if they can speak. If he can't, maybe another part can buddy up with him and speak for him. I have a young one who can speak for the little ones if needed.