Help with 02 Rear Audio

I have a 2002 Envoy SLT. About 2 months ago, my passenger side power seat + (heat) and rear speakers stopped working. Checked all wiring under seats and fuses and no progress. Also checked fade and balance controls on head unit, front works fine and nothing from the rear. Stereo system is all factory, no modifications have been made to the vehicle.

Searched a thread in regards to power seats for the Envoy and the power seats + heat are now working. I was hoping this would resolve the rear speaker problem, but they are still not working. Is there anything else I can check before I start taking my rear doors apart?

Thanks in Advance