I just bought a 04' GMC Envoy that has a stereo in the backseat that runs through the stereo in the front. If you hook up an aftermarket stereo how can you do it to still have the back radio still work.
you cant splice the wires when you hook it up. you have to go to an auto parts store and buy a 5 dollar wiring harness for your year of gmc and it will all work. and it is easy to install all the wires are marked.