WARNING: This page is about a different car, the 2018 BMW 340i, 2017 BMW 340i, and 2016 BMW 340i. However, it is still accessible from the selected car via links, so may be relevant.
Fasten the flywheel with the special tool 0 493 938 (11 9 260) and tighten with the special tool 0 494 130 (11 9 264).