service airbag

Hey everyone, I have a question that I haven't found any answers on. I purchased an 08 LS 5 speed with 104,000 miles for 1500 bucks to drive as my beater with a heater. When I picked it up, the only light that was on was the TPMS, which wasn't a big deal to me. A couple days later, driving in...

i drove my 2008 chevy cobalt LT sedan home from a 45 min drive, no lights no problems no codes, worked perfectly, then in the morning as soon as i started it my airbag light came on and "service airbag" was shown, since then the light has no turned off and the passenger airbag is working...