Breaking news
The serial interface of the changer (so probably the HU too) can be connected directly to an rs232 port.
See the second post (by CristianC) in
this page.
Not that I understand romanian, but it seems this folk connected
directly the changer to a pc rs232 port and saw this: 3D 01 FE FD 3D 01 FE FD 3D 01 FE FD.
Sounds familiar?