Rear window button
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 front electronic module (FEM) is the master control unit. In other words, the front electronic module issues the enable for opening the rear window.
Pressing the rear window button switches the microswitch to ground.
When the rear window button is pressed, the rear electronic module transmits the request to the front electronic module. If all the preconditions for unlocking are in place, the front electronic module issues the enable for opening the rear window. For unlocking the rear window, the rear electronic module activates the DC motor of the release drive in the rear window lock.