Sounds more like an i-bus problem.

e46 Verts are prone to water ingress into the boot mate.

Things to try:

1: disconnect the phone module (if you have one), and try the system.
2: disconnect the cd changer, and try again.
3: disconnect the radio module, you will get no sound but the screen **should** still work.

If still the same reconnect and then...

If you have a mk3/mk4 and TV module, then...

4: disconnect the TV module and try the system, if working TV module Kaput.

Then (if TV module makes no difference).

5: power down the mk3/mk4 (correctly) and then disconnect it and bypass the nav computer by plugging in the blue lead from the nav into the blue plug of the TV.

again, if working Nav module Kaput.

If all this has no effect, then the HU is Kaput (probably).

Testing the components individually narrows down the module that's broken.

Doing the donkey work yourself saves money if you have to take it to a dealer.

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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.