Mercedes B Klasse Hybrid Bluetooth Audio Issues

That sucks about your Merc's audio system. Defective infotainment systems aren't exactly unheard of, especially with all the tech crammed into modern cars. Before dropping 815€, did you try anything simple, like checking the Bluetooth connection thoroughly or doing a system reset? Any luck with the volume control outside of phone calls, like radio or media playback? Does the error code give any more specific info?

I tried the basics. Unpaired and paired the phone several times, even tried a different phone. Factory reset the whole infotainment too. Volume control is wonky across the board, and speech recognition is totally deaf. The error code is pretty generic, something about 'microphone circuit malfunction'. Any thoughts?

Generic error code AND volume issues across the board after a factory reset? Sounds less like a simple Bluetooth issue and more like the whole audio system module is fried. Sadly, that 815€ microphone repair quote might just be the starting point. Get a proper diagnostic at a reputable shop before throwing parts at it. Could be a deeper problem.

Thanks for the advice. I took it to the workshop. You were right – the whole infotainment unit was the problem. Ended up costing the quoted 815€ to replace. At least the hands-free microphone, volume control, speech recognition and the whole audio system are working again!