What you will need:
OBD2 Scanner that can diagnose BMW SRS Module
Locate OBD-2 port under the dash. Connect your scanner to the OBD2 port.
Turn on ignition. Don't start the engine.
The scanner will turn on. Select your BMW chassis/model on the scanner.
Select BMW - Control units - Body - Safety System. Once you navigate to Safety System /SRS control unit you can read Airbag Fault Codes.
Clear codes from the airbag control unit. Go back one menu. Scroll down to Clear Fault Codes. Press YES in the next screen.
Airbag codes can only be erased if the code is in stored status. Meaning the fault is stored in the memory of the SRS unit but the problem itself no longer exists.
If you didn't fix the problem that triggered the airbag light/code, you would not be able to clear the codes. They will return as soon as you restart the car. Read the codes again and fix the problem. Then reset the airbag light again.
Most airbag fault codes require a scan to clear the code and reset the light. In very few certain circumstances, the airbag light will turn off once you fix the underlying problem without the need of scan tool.
Disconnecting the battery will not reset airbag light or clear codes stored in the airbag control module/SRS system. Generic OBD2 code readers can not clear BMW airbag light.
Always disconnect the battery before working on any airbag component.
When handling airbags always keep your body two feet away from the airbag.