Stew, I think since mine is a 2013, it was not wired that way since I have the safety plug "box" in the overhead that the TV plugs into - the TV would not turn on (or power off) when moving, so easy to bypass, just unplug from that black box and plug into the other plug. These new(er) units don't seem to use that power feature to disable the video.
Found a work around. (love U-Tube) I don't recommend this, but I just tried to see if it would work.
There is a "Parking Brake" wire in the main plug wiring harness in the back of the unit. If that wire is unplugged, and tied into the ground wire of the radio, it will display on the TV.
Of course, I left it alone.