hish747

On my 2012 W204 the Radio/Phone/USB makes no sound. Here are the details:

-The head unit seems to function normally (Radio changes channels/inputs)
-Music looks like it plays from a USB stick.
-The iPhone connects via bluetooth and can dial out. People I call can hear me.
-I'm not sure if it matters, but connecting my iPhone via the USB doesn't register anything as connected. Maybe this is normal?
-Navigation system works and seems to accept voice commands but I can't hear any guidance.
The volume dial does nothing and neither do the steering wheel volume +/- buttons.

When I unplug the amp fiber connection, I see a red light momentarily that goes out about a second after I see it.
When I unplug the satellite radio component, the same thing happens where I see the red light and then it goes out.
I tried bypassing both components with a fiber loop/bypass but sound did not return.

Does the fact that music plays from USB mean that the media interface is fine? Or should I just remove the glovebox and check the media interface anyway?

I feel like I should suspect the amp may be bad. If I buy a replacement same model on eBay would I need the dealer to program it?

Any other diagnoses I can do? Is there a way engineering mode can help me figure where where a potential break is in the fiber loop?
Thanks,
Hish

hish747

Problem solved. It was the pesky media interface module. Bypassing for now.