No sound coming from speakers until I turn off the engine

[Cfields1973$]

okay here goes. I just recently baught a 2000 jimmy sle 4x4. I wanted to replace the head unit so I went ahead and removed the old and was getting to ready to install the new. to my utter suprise wich sounded like "you Gotta be F****i*g kidding me!" I noticed that either the low life car dealer or the uninformed previous owner had removed the factory wire harness. I figure no biggie right? how hard is it to match colored wires? well long story short, after a whole lot of cussing and why the F wouldn't gm make its color wire scheme uniform to other companies. anyway I finally got it wired correctly? now theres no sound but power to the unit lets me know it works. the only time any sound comes from the speakers is when I turn the ignition off. I get a quick like second of static when i do. I'm just wondering if its a bad ground issue. I'm about to tighten up the quick, and to be honest excited wiring I did. if anyone has info that I'm not able to find through Googles everything but the year, make, model, and issues search that only returns results for vehicles made 20 years before, or after the year your looking for, or 1 year before or after your model year. Id appreciate any help or suggestions offered.