2003 Monte Carlo New CD Player Problem?

I have tried to install an aftermarket headunit, but the unit doesn't get any power at all. I used a cheap wiring harness and others suggested a different harness GM09SR on sonic electronix's website. The harness may be the problem, but when I tried hooking up my old stock head unit which functioned without problems it doesn't get power either. Could it just be a fuse if so what fuse?|||This car is a Data Bus car and you need to get the expensive harness with the data bus electronics built in . there is no ignition wire in the factory harness . the factory radio is turned on by a digital signal on the data bus wire. you can create your own ignition wire if you know how to properly wire it but its not something for a shade tree to try. The factory not working may be a blown fuse just check manual, if not it may be a data bus problem . the factory radio is programmed with the VIN and the computer checks it through the data bus every time b4 it allows it to turn on. dumb huh?! 15 years in car audio, and heard of only @ 2 factories ever stolen.does this help?