1) Quick-connect coupling with ID marking: Removing
WARNING: This page is about a different car, the 2012 BMW 328xi, 2011 BMW 328xi, 2010 BMW 328xi, and 2009 BMW 328xi. However, it is still accessible from the selected car via links, so may be relevant.
Push quick-connect coupling (1) against pipe (4) (thereby relieving strain on spring (2)).
Press plastic ring (3) into quick-connect coupling (1) and remove coupling (1).