51 26 020 Replacing switch (central locking drive) for tailgate lock (Z3 coupe, M coupe): Installation:

WARNING: This page is about a different car, the 2002 BMW M Roadster, 2002 BMW M Coupe, 2001 BMW M Roadster, and 2001 BMW M Coupe. However, it is still accessible from the selected car via links, so may be relevant.