1999 chevy tahoe rear speaker problem

i have a 1999 chevy 4-door tahoe without onstar. It has 6 speakers in all (front doors, rear doors, and far rear roof). I have a Pioneer DEH-5900IB reciever that i installed myself and i have come across a major problem. I purchased the wiring harness and soldered and heat-shrink tubed all the corresponding wires together. I hooked up everything and when i use my new reciever, only the far rear roof and the front door speakers work. No sound comes out the rear door speakers. When i removed my new reciever and put the stock reciever back in, all speakers work again. Then, i hooked up the new reciever and the rear speakers no longer worked. I looked at the speakers themselves and the wires are connected and fine. However, on the radio harness, there is not a set of wires that go to the rear door speakers, yet they still work when used with the stock reciever. I am very frustrated and any help would be much appreciated from i just spent $250 and not all the speakers are working.

there is an amplifier connected to those speakers.  You need to connect the Blue/White wire of your radio to the Blue wire of the harness you bought.  The blue wire should be labeled power antenna.  You do not have a power antenna so you assumed you did not need to connect it.  Happens all of the time.  Enjoy your new radio.