Any ideas on how to diagnose? I have an 05 Allroad. Sub works and swapped out stereos and still no go.

Thanks

 

explain your stereo set up thoroughly. I might be able to help.
I'm assuming u have an aftermarket stereo installed in your car. Did u buy a wiring harness for the stock stereo wiring harness to your new stereo?
When i installed my in-dash into my 02 B6, i noticed that the rear speakers used RCA inputs. Kind of confusing but it works. Also notice that the front speakers are a lot louder than the rear speakers and sub itself.

I can take some pics and post it up if u need me to show and clearify things more in detail of how i hooked up my stereo.