I have a old CD player that came stock in my 2003 sonoma ZR2. I want to rig it up to a inverter in the barn to play some tunes while I work on vehicles. But I lost the harness. Is there a way I can use a ohm/multimeter and figure out which one is the power pin, and which is the ground?

 

Why not hit the auto wrecker and grab a harness from a vehicle? The Install Doctor - The Do-It-Yourself Car Stereo Installation Resource for info on the wiring.... it might be on that site.