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Belt buckle switch

The belt buckle switches indicate whether the seat belts have been fastened or not. The belt buckle switches are supplied with clocked voltage by the airbag control module. The following shows the voltage curve that is measured at the airbag control module when the voltage curve is OK. For the voltage measurement, the adapter lead must not  be connected to the seat belt buckle switch!

Fig 1: Belt Buckle Switch Operation Graph
G09910178Courtesy of BMW OF NORTH AMERICA, INC.

Test image for oscilloscope measurement 

NOTE: All work on the airbag must only be conducted with the battery disconnected! Connect and disconnect airbag control module, sensors and gas generators only with the battery disconnected! The airbag control module contains vehicle-specific data and must therefore be encoded before placing into operation! Removal and installation in other vehicles is prohibited!