prodigy p 2 brake controller

1st. disconnect the trailer to isolate the SH. If SH remains when trailer is disconnected you have a short somewhere within the prodigy and vehicle wiring. if no SH when trailer is disconnected then plug the trailer in and check, if SH shows then you have a short either in the connection at the Vehicle and Trailer or a short in the trailer most likely the brake wiring where it runs along the frame and axles.