Functional description, see BMW Service Technology:
TIS -> Document -> SI Technology -> SBT Number (650505138)
When terminal R is activated, the airbag control unit is supplied with voltage by the Car Access System and a system self-test is carried out. During the test, the airbag warning lamp in the instrument cluster is activated for around 5 seconds. When the system self-test has been concluded and no fault has been detected, the airbag warning lamp goes out. When the system self-test has been concluded successfully, cyclical fault monitoring is carried out. The cyclical monitoring runs internal diagnosis of the airbag control unit as well as of the entire safety system.
When the driver or front passenger has not fastened a seat belt,
For customer who mainly use their vehicle alone and transport objects on the front passenger's seat, the seat belt warning would issue continuous alerts. For these cases, the seat belt warning can be disabled for the passenger's side in the workshop by means of coding. The visual warning via the seat belt warning lamp remains enabled.
Note:
All work on the airbag must only be conducted with the battery disconnected!Connect and disconnect airbag control unit, sensors and gas generators only with the battery disconnected!The airbag control unit contains vehicle-specific data and must therefore be encoded before placing into operation!Removal and installation in other vehicles is prohibited!