The box you labeled as TCU is a combox. It replaced the TCU and or MULF from late 2011 on. The box in the front is the amp. The sat receiver hardware is built into the head unit from 2010 up. Is there fiber going to the amp? I think that is the base system which should function even if there is an issue with a component on the fiber loop. The logic 7 amp uses fiber and audio is lost if there is a fiber issue.

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2009 35d, 2006 325i & 330i