Just happened to me a few days ago. Have an appointment set Monday. Bass is gone. They told me to check my battery and make sure it was fully charged. I trickled it all night and still no bass. Premium isn't sounding so premium! Frustrated.
They just had to replace both of my motor mounts last week. I was getting a pretty gnarly sound under the hood at WOT.
2011 E92 M3 DCT | Le Mans Blue | 19' Volk G12 Gloss Black | H&R | ACM Testpipes | ESS Tune