Since the message was intermitant, I have held off replacing the wheel bearings. I recently bought this 2005 SV6 with 100k miles. It has started just fine in very cold weather, but the battery had some years on it. First I cleaned the contacts in case that could cause a problem, since the battery tested ok one time and not another.the sensors are built into the front wheel bearings so they are subject to heat and other environmental conditions. the other cause is the wire harness attached to them can deteriorate.