thanks for replying. the harness I'm using plugs into the factory harness, so that I can reinstall the stock deck by just plugging in the old plug. (It's a Lexus, not a BMW)

I'll check the docking connector and I'll try running a line direct from the battery tonight.

I hope it works, I've wasted so much time on it. If it doesn't, I'm gonna give up and buy a new deck.