WARNING: This page is about a different car, the 2018 BMW X5, 2017 BMW X5, 2016 BMW X5, 2015 BMW X5, and 2014 BMW X5. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Overview Of Steering
Courtesy of BMW OF NORTH AMERICA, INC.
Overview, active front steering
Overview, Dynamic Drive
Bleed hydraulic steering
Carry out steering angle sensor adjustment/adjustment for active front steering