Woo I got my unit now. And it works, kinda. Screen comes on, I can navigate with MMI buttons, etc., and the Audi menu comes up too.

But the car won't start. :( I get a bunch of faults with I turn on the ignition: parking brake, ESC, tyre pressure etc., and the engine stops after a second or so.

If I remove the CAN connector the car works fine, so I'm guessing it's a CANBUS problem. But how would I troubleshoot it?