One problem related to lose power steering has been reported for the 2015 Audi S5. The most recently reported issues are listed below.
My 2015 Audi S5 is getting faults on the steering after driving in the rain one night while driving a red light turn on and had lose all power steering and was nearly un-drivable. Description NHTSA recall number the affected vehicles have electric power steering assist systems that may shut down as a result of a steering motor sensor fault (which could only occur with very cold ambient temperatures). If the vehicle experiences a loss of power steering assist, extra steering effort will be required at lower speeds, increasing the risk of a vehicle crash. 15v452.