New Radio, engine code reader issues

Currently I can not get a code reader to read my engine codes. I get a link error. On many different readers, the first time this happened was after I pulled out the useless onstar unit. Well I replaced it after removing the GPS. Now after I put the new radio in with the $20 harness, and I put in the radio Pioneer Premieer DEH-690somthing, I plug in a code reader and the onboard informaiton system says airbag problem, serv stability system, and either low oil pressure or coolant. But I still get a link error. Sombody told me I have to buy a door chime module but I am really enjoying the chime free enviroment, and the thing is $100 DOLLARS! Plus after removing the factory radio, the harness that is normally used for that info was non existant, does this data commune over the same single radio harness? The airbag problem scares me I heard a rumor about some guy whos airbags went off with a small hit on the bumper sensor. He was tying his shoes and bird hit the bumber while driving foward. The impact detonated airbags and then reflexes or somthing stoped the car, but he died from his neck being broke. (RUMOR) I think this is an exagerated urban legend but probably came from the airbag issue. Any info on this thing, or is my onstar unit not functioning again.