The BC should be working mate, are you getting info in the binnacle when you press the button? or has this stopped.

Do you have an i-bus enabled device plugged in(like a dice or intervee)?

Power down procedure.

Go to the car open the drivers door,
Then go to the nav computer, press eject on drive,
Eject the map disc,
Wait for the red led on the drive to go out,this could take 3-4 minutes, (do not open or shut the doors or toggle the ignition).

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Sept 03, M3, Silver Grey. Retro-fits: Modded Mk4 DVD Drive, OEM Bluetooth, VR Control, Rainbow Speaker Upgrade, Sony SOT Amp, HK Sub, CCFL, Intravee II, NightMode.