31 00... Information on replacing shock absorbers: Situation
WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2012 BMW 328xi, 2011 BMW 328xi, 2010 BMW 328xi, 2009 BMW 328xi, and 2008 BMW 328xi. However, it is still accessible from the selected car via links, so may be relevant.
When a shock absorber is faulty on one side (leaking, noises, limit values exceeded on the shock tester), often both shock absorbers on the axle in question are replaced.