99 dodge, Pioneer DEH-P80MP no sound

I have a 99 Dodge Ram 1500 extended cab SLT Laramie edition pick up (top of the line, fully loaded from the factory, leather etc.). I think it has the infinity sound system due to the extra stock speakers, but I am not for sure. It has the 2 rear speakers 2 front door speakers and a pair of tweeters mouted in the window frames (not sure of proper term). This is all stock. I tried to add a Pioneer DEH-P80MP head unit and I get no sound from any of my factory speakers. I bought the wiring adapter I assume is the correct one from Best Buy with the head unit. The thing that is strange is that I get sound from my Subwoofer outputs that I have connected to my Rockford Fosgate amp though. I changed back to the factory unit and it works though. Also I connected the wires as it was directed on the wiring harness to the head unit. Is there any chance that there is an amplifier that came with the truck, and I need to bypass it? If so where might I find it. Any help is greatly appreciated.

there is an amp in your truck try hooking your blue and white amp turnon to the blue wire for the power ant on the harness that plugs in to the truck. that should fix it.   

No to the amp bypass, yes to the above advice with a twist. Some head units have both a blue and a blue / white wire. One of these wires is the power antenna trigger wire, the other is the remote on trigger wire. You want to use the remote on trigger wire and attach it to the blue wire on the harness adaptor that plugs into the factory wiring harness.Top Secret, I can tell you but then my wife will kill me.

I got it thanks for the help. I hooked the remote to the antenna.