Ok here I did so e research. Check out this link. Read through it because they talk about it. And by the way, this is a great website for info on these units.
Basically the relay works but it doesn't work, due to how the radio checks for the parking brake. It doesn't check at turn on like the earlier units, it only checks when you turn to a video source. So start a DVD as the source, then turn the radio off and back on. It should work.
To fix it you can either get a switch or an aftermarket bypass from the website listed in that thread, I think microbypass.com but I did not read the whole thread. So you should do that.