Roller sunblinds on the rear driver's side and rear passenger's side
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 roller sunblinds on the rear driver's side and rear passenger's side are each connected to the junction box electronics via a LIN bus.