it shouldn't have onstar...that is some bull...should have told the guy u didn't need all of that junk...how much was the harness you already have ( the one that doesn't fit? )...you should just straight wire it into the radio's channels on the back of the HU, thats what I had to do with my car, and I have that $120 dollar one for my 06 but thats the only one they make for my model...