1. From the main iDrive screen, hold down the knob for 10 seconds then let go.
2. Turn clockwise 3 clicks
3. Turn counter-clockwise 3 clicks
4. Turn clockwise 1 click
5. Turn counter-clockwise 1 click
6. Press down the knob (don't hold, just click it)
Within a few seconds the screen will turn blue and you can enter diagnostics, but as far as we can tell, it doesn't show the version number. There is one field that looks like it, but I've been told it's not, just coincidence.
2010 Mercedes-Benz C350 4Matic
2006 BMW 330xi - Gone