The H/U will have a black wire that is suppose to be connected to your ebrake , so when your ebrake light comes on it closes the H/U curcuit, which will allow you to watch the screen, a dvd will still play without the video if the ebrake isn't on, what you can do is just ground that wire to the chassis, or you can bend the the ebrake tab back so it reads that the ebrake is on so you can watch while you drive(you don't have to hook it to the ebrake but if installed by a dealer then they have to or they could be sued, it is a safety hazard tho.im still sorta confused on what u meanby grounding it. im guessing a wire coming off the headunit, for the screen itself and just ground it with the headunit ground?