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Discussion Starter · #1 ·

Due to a previous problem with intermittent power supply issues that was due to corroded battery connectors (see this thread) I got a secondary fault with a dead head unit for the audio system on my 2009 120D (E81). I am trying to narrow down the problem and see what my options are to either replace faulty parts or upgrade to a more modern audio system at the same time.

I have the BMW audio professional system with hifi speakers, multi-function steering wheel and USB interface. No phone connection, iDrive/Navigation, CD Changer, DAB, bluetooth etc. Its the LCI version of the E81 (which is the 3-door version of the E87).

The radio is totally dead, no audio, no display, no PDC or other warning sounds etc. It seems to get power, though, as there is the buzzing noise when pressing the eject button for the CD player.

Checked all the audio related fuses, including the fuse on the back of the radio. All were ok.

I suspect that the main radio unit broke due to the power supply problem and now needs to be replaced. I suppose there might also be a possibility that there is another component in the MOST fiber optical network that could be broken.

I checked the fiber optical connectors going in/out for the radio as well as for the USB interface and there is no red light in any of them. The amplifier behind the trim in the boot seem to have no fiber optical connector. Haven’t been able to figure out if there are any additional components on the MOST bus I could check, just to be able to narrow down the problem to a faulty radio unit. Anyone knows where to look or if there are any schemas of the MOST network to check?

If the problem could be narrowed down to a faulty radio unit, they seem to be quite expensive and difficult to find, so I was thinking that it would be a better option to upgrade to a standard aftermarket unit with navigation, apple carplay etc. I wonder if that could be a viable option, if I could use existing speakers, hifi amplifier and get PDC warning sound without having to do a a lot of rewiring, maybe even to be able to use the buttons on the steering wheel?
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