BKR3

Hello mbworld forumers, I've been reading stuff in here for a while now, I don't really do interesting stuff worth posting nor do I have the experience enough to help others, this forum has helped me out not once. But this time I can't find similar problem to what I'm having now so I decided to sign up and ask the question.

So the problem is the tapping/knocking noise from engine while key is turned but engine isn't running. It's not consistent/stable it's random and sounds like small metal parts bumping. I was told that it is the turbo geometry adjuster going back and forth which it shouldn't be doing, otherwise car runs fine and the adjuster does just fine when engine is running. I think it must be the electrical problem but what do I know. So if anyone has encountered this problem please share your experience/knowledge. Many thanks in advance.