Code letters on crankcase
WARNING: This page is about a different car, the 2010 BMW 135i, 2009 BMW 135i, and 2008 BMW 135i. However, it is still accessible from the selected car via links, so may be relevant.
Code letter A = bearing shell (1) color Yellow.
Code letter B = bearing shell (1) color Green.
Code letter C = bearing shell (1) color Red.