Sony CDXL510X into a 1999 GMC Suburban

trying to install a Sony CDXL510X into a 1999 GMC Suburban.  I used the wiring chart for the Suburban on this sight and the wiring chart for the Stereos harness from the sony manual.  The problem is once everything is powered up I have only the right front door speaker and the right 6x9 in the very rear working the other four speakers are dead.  Any ideas what the problem could be or where I might have went wrong??????

disconnect all of the speaker leads, meter each pair of leads to see if you have 4 matching pairs of wires that read somewhere in the area of 4 ohms. once you have done this, take a small battery (AA or up to 9v) and connect each pair of wires to the terminals on this small battery for only a fraction of a second. Make sure that you have a speaker resistance showing on these wires! You should hear a pop from the speaker. If you do not get a pop you may have the wrong speaker wires. If you do get a pop then listen for it's location and hook it up to the proper wires on your baloney. Make sure that you have the polarity correct on the speakers, you don't want them to be out of phase. Repeat as necessary for all other speakers. Did all the speakers work before you started on this, was the factory player hooked up to it?Top Secret, I can tell you but then my wife will kill me.