HERE I will show you how to properly diagnose bad MOST bus unit and successfully bypass it!
Standard problem-no sound, bmw dealer diagnosed bad amp and wanted 1900$!! All was fixed in 5 minutes under 30$. Bad unit turned out to be sat tuner module, which was bypassed. If you don’t listen to xm radio you don’t need the unit, if you do - buy another xm unit.
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fiber optic bypass loop jumper:
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