If you are considering a replacement, it is important to know the differences between the B3 and B5 modules:

For more information on the Siemens BSM B3 schematic and related topics, consult the following resources:

Power supply for front fog lamps, headlights (dipped and large-scale), and turn signal repeaters. Fuel & Engine:

The BSM acts as the nerve center for power distribution under the hood. It relays complex digital signals from the main body computer (BSI) into high-current power execution for engine components, lighting, and pumps.