I've done a scan on all nav/radio modules and it show my nav-computer, the radio module and the monitor.
Setting the ignition key to 1 gives a lot of data.
All kind of status request and data transfers.

If I read settings from the navcomputer it tells me it's coded to a E39 and the languages GB and FR. As far as I can tell it's reading data from the Ibus.
Coding the navigation gives a few entries in the log window.
This is in my log.
21-4-2007 20:19:25: Original settings read from nav = 00 FF FF FF 00 00 00 00 00 00 00 00 02 01
21-4-2007 20:19:25: New settings written to nav = 00 FF FF FF 07 06 01
21-4-2007 20:19:32: Code Nav Settings - Error when coding nav with new settings: Timeout (no response)