Hello,

I am installing an aftermarket stereo on my cooworker's 2004 S40 1.9T. I've installed stereo's in several other cars with no problems but this one has been cursed from the beginning.

BestBuy sold us the wrong wiring harness and after ordering the correct one online and installing the stereo, only the two front dash speakers work. The front door speakers and the rear speakers do not work.

Is there a factory amp that needs to be bypassed or something? If so where is the location of the amp? I could not find it.