Door contacts
WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 2017 BMW X3, 2016 BMW X3, 2015 BMW X3, 2014 BMW X3, and 2013 BMW X3. However, it is still accessible from the selected car via links, so may be relevant.
The footwell module (FRM) detects the signals from the door contacts. The footwell module forwards the signals via a bus connection to the Car Access System (CAS) and the junction box electronics (JBE).