I have a 2001 merceder ml430. The scanner says that the crank shaft sensor needs to be replaced. I have replaced it twice and it is doing the same thing.

I'd suspect system ground...computer is having trouble finding ground...you must take the other end of the clamped 1/0 battery cable [the one that attaches to the frame] unscrew and wirebrush the connection clean, so that the 300 cold cranking amps can get through there...the connection to the motor block (near the alternator usually) as well~...get a new battery if older than five [knock off labels on top of the battery]~