THE VEHICLE LOST POWER STEERING IN A TURN AND THE DRIVER HAD INSUFFICIENT STRENGTH TO CONTROL THE VEHICLE. THE VEHICLE DROVE OVER THE CURB ON THE SIDE OF THE ROAD AND BENT THE TIRE RIM. THE DISPLAYED CAUTION WAS "POWER STEERING ASSIST FAULT/ SERVICE ADVANCETRAC." IN A DIFFERENT SITUATION, THE CURB COULD HAVE VERY EASILY BEEN ANOTHER VEHICLE OR PEDESTRIANS. THIS FAILURE OF POWER STEERING HAS OCCURRED AT HIGH SPEEDS AS WELL. SERVICE PROVIDERS DO NOT SEE THE FAULT IN THE WORKSHOP AS THE FAULT CLEARS EACH TIME THE CAR IS TURNED OFF AND FAILS RANDOMLY.