I too am having a similar problem. My camera works when I put the car in reverse and select the reverse camera option on the HU, but it won't turn on automatically when engaging reverse. It also won't show the guide lines. I have the AVH-4200NEX. The rear camera is powered by the reverse lights and the ground wire is grounded. The RCA cable is routed to the brown BC plug in the HU. There is also a red wire coming from the RCA cable to be plugged into the reverse cable (violet/white) of the HU if needed, which isn't plugged into the car. Out of desperation I connected the red wire to the violet/white wire but still nothing. Any help would be appreciated in getting it to automatically turn on. Thanks.