have you fitted new controller and had them programed. i had code 51 last week. see the little blue current limiter that bridges across the line contacter ,that allows the capacitors in the controlers to power up before the controller will pull in the line contacter. watch out it may be hot. you could try dissconnecting battery and discharging system by pressing the horn ,leave it for 15 mins then try again. a lot of key on/offs can cause this fault code to kick up