Both rear power windows on my 03 EXT stopped working at the same time; driver's console will not operate them either. Front windows work fine. All Fuses check good. Any ideas?

Master switch one issue, window control module another, get it checked out to avoid expensive parts changing.

I pulled off the Master switch (GM part# 15180052) I do not have a wiring diagram, but I measured the voltage at the various orange wires. All measure 12.4V except no reading (0V) on the thin orange wire on the middle connector. Would this indicate a bad switch? Is a wiring diagram available?

Yes go to autozone.com, repair guides.