Hi, Roger has good idea, allways have proper diagnostics check. I purchased X5 with 43k so i do not know car history.I do know that some one replaced left front cv boot because that wheel and all surrounding components were covered with grease.When doing that repair,the wheel bearing is removed and it has impulse wheel attached,which could have been damaged. Even though diagnostics said sensor fault i still worry that impulse wheel could be faulty. Another possible cause is brake pad wear sensor as the one fitted to car was not correct length and it stretched baring wires which may have put power spike through hub thus sensor, causing fault code.Dealer replaced pad wear cable at first fault code. The second time i got malfunction, the pads were nearly worn so the power spike could have been pad sensor but i doubt if pad wear sensor causes such problems unless speed sensor also defective. So new pads to all wheels,new pad sensors front and rear, new speed sensor left front and hope for the best. So all you people with similar problems may want to have correct diagnostics check done and take it from there what could be done to fix.Wish you all good luck.