Just a thought but have you driven it, while driving is the light coming on and then going off? I know a guy who had his steering wheel off and after he re-installed it his light was going on and off so he called to ask if my shop's star machine would work on our cars. I talked to one of our MB tech's (Sprinter) and he advised him to unbolt the airbag without unplugging it and make sure the plug was secure and after he did that his car was fine, maybe the plug wasn't tight. I know if you start the car with it unplugged it takes a star machine to clear it but you might try checking the plug.