I have a 2004 Audi A4 and the tape player was working fine as well as the radio. I took the tape out and hit the CD button and got Error 3. After that the Unit would no longer take the tape or would the radio play. The unit turns on and everything but no audible sound. I pulled the fuse for the radio and turned on the car and the buzzing sound was gone. Put the fuse back in and the sound is back. The sound goes up and down with pressing and releasing the gas and it is coming out of the speakers. Any idea what is going on? This sound drives me nuts..

 

Same problem here. B6 1.8
I unplugged the connection from the back of the HU to disable the speakers. Annoying static/engine acceleration sound.

Still looking for a fix.

Thanks.