Installed Pioneer DVH 5000 in 98'Suburban

As some of you may already know, I recently got into installing audio in my 98' Suburban (with no onstar).  I installed the Pioneer DVH 5000MP indash DVD, CD, MP3 receiver in conjunction with the Alpine TMX 680A overhead TV monitor.  The unit works fine, but with only one problem.  My rear door speakers do not work.  My front speakers and rear barn door speakers (by the rear roof headliner) are working.  So 4 of 6 speakers are working.  I can't figure out why the rear door speaker's don't work. 

I used an aftermarket radio harness for the install and I connected all the wires from the harness to the Pioneer reciever except for the blue wire (remote amp wire) because I didn't install an aftermarket amp. 

Did anybody have a similar problem when they installed their aftermarket radio?  And does the 98' Suburbans come with a factory amp?

Any feedback will be appreciated.  Thanks.

Just hook up the factory amp turn on wire in teh harness.  The rear doors are run off an amplifier underneather the driver's seat.