I suspect the speed sensor but no more than it does it I haven't bothered to replace it yet. Mine only does it once about every thousand miles or so, also seems if I stop the car and met it sit for a couple of minutes it will start working again. I read somewhere that if the speed sensor fails it will also affect the power steering, something to do with the feedback from the sensor controls the power steering pressure. I am not an expert but I am sure one of the more knowledgeable peeps on here can provide feedback. Good Luck