Hello all. I recently installed a new head unit with DVD and am adding a backup camera. I have the camera installed, including powering the camera from the reverse lights and the RCA cord is connected to my head unit. I now need to tap into the reverse light wire from the head unit so that it knows when to switch to the camera when I am in reverse. Where is the best (easiest) place to tap into this wire? I have an 05 Envoy XL with 4.2L.