I recently installed the Pioneer DEH-P400UB Headunit and was able to get the unit to turn on. For some reason I am not able to get any sound out of the speakers. I reinstalled the factory unit and the sound works fine. Now, I didn't get the antenna adapter because I didn't ever use the radio with the factory unit and figured no need for this one. One member suggested that I need to use the blue wire and route to the amp.
My stock system was the Bose 6 speaker w/ factory amp