it means there is a fault n ur air bag system,ur airbag may not work,its a saftey device ur computer has a code stored n it n an accident accident investigators an ins agents can access this info to denyy claims,some places,shops etc wont even get n ur car 4 fear of air bag going off.dealr will rob u,i have a m/b,i no but a certified bmw shop needs to chk it,not nesscarily bmw but 1 that specializes n bmw.u can disconect the battery for a few seconds that will reset the computer but if there is an actual fault lite will come back on