You need to buy a reset tool for the SRS
What is the SRS light trying to tell me?
The BMW SRS light can mean any number of things from serious to minor. Sometimes it's alerting you to the real need for a repair of a broken part, but sometimes it is merely indicating that a circuit critical to proper SRS operation was temporarily disconnected (i.e. while you were installing a stereo, alarm, racing seat or steering wheel).
Here ya go . .
http://www.bimmerzone.com/BMW_SRS_Airbag_reset_tool.htm
Good Luck ! !