it could potentialy be a blown channel in the radio, i would pull the radio out and try to test the speaker at the wiring coming from the radio with a "AA" battery to see if it pops and then go from there. I see your in illinois, if your near southside chicago im an MECP installer, you could swing by and I could help you out with some troubleshooting if you cant get it.
Steve Pitts Jr.
-edit I take that back if it was a blown channel the dash speaker wouldnt function either. I'm goin with faulty speaker wire or speaker connector .