Nathaniel H

I have a 2001 Mercedes E320 wagon. The previous owner took the stock Bose radio and CD changer out and stuck a POS $100 pioneer in the dash. It looks like they did a good job, they used an adaptor and everything and I think they are using stock amp but is sounds terrible. The tweeters and dash speakers do not work. I did not see any wires missing from the stock radio to POS adaptor except two. Do you have any ideas? A wiring diagram for the stock stereo plug would be very useful. I would replace the POS with the stock stereo, but those are like $700 and I don't have the money for that. If you need any pictures, just ask.

Thank you,
Nathaniel