2001 sunfire

What are you trying to do?  Install an aftermarket head unit?  Are the factory plugs still intact?

when you said "sunfire cd player" I'm assuming you mean the radio/cd player unit as a whole?  The sunfire's radio uses a Class II wiring connector that looks like this, but the grand prix's connector is the standard '90s GM connector.  Technically you could match up the power, ground, and 8 speaker wires, but your problem is going to be the turning on of the head unit.  I THINK that it would work to just match up those aforementioned wires; you'll just have to turn the head unit on and off manually as it will not be tied to the ignition like most radios.

Someone please correct me if I am wrong in my assumption, but I was under the impression that all of the Class II radios were the kind that don't need the key in to be able to turn on the radio.  And that the only reason they turn on automatically when you turn on the car is because it gets the data signal to turn on.  but as I understand it, the data signal is not REQUIRED if you don't mind manually turning it on and off.  If that's the case then yancy will have no problems installing the head unit, but part of me is thinking that that was only the case with the '02-up RDS radios.

Oh well it certainly couldn't hurt to try it.  Unfortunately I've searched everywhere and can't find the wiring colors for the sunfire.  So the best thing I can suggest is to look carefully at this picture of the harness that plugs in to the female plug that's part of your sunfire's radio wiring,  as well as the picture of the '90s gm wiring harness, and see which wires match up where.  Hopefully you haven't cut off the plug from your grand prix yet...because it'll be easier to just use a wiring harness to connect to the factory plug.  Then the bare wire ends of this harness will go to the bare wire ends of either a GM class II reverse harness, or the plug that you cut out from the factory wiring in the sunfire.  The problem is that I can't find a good color picture of the reverse harness, so the best I can give you is the picture of the harness that would go on the other end.   You're going to need to verify all your wires with a multimeter (and possibly also a speaker popper) regardless of how much info I give you, but looking at those pictures should help get you started.