I have been having Servotronic Failure fault intermittently over the past four weeks. It caused the steering to become very heavy but usually cleared on complete switch-off and re-start. Over the past few days it has refused to clear. I read that it migt be related to battery weakness and was wondering if I briefly disconnected the battery would this help (or cause more issues).

NB. 520D; 6yrs old; 53K miles - battery replaced 2yrs ago.

 

I had the same issue here. I replaced my battery with an AGM battery and that seemed to fix it.

 

Got new battery (not yet coded to car); still getting "Servotronic Failure" error