I was driving on snow/ice covered roads today. Temp was hovering near zero but there was some moisture coming up off the road which was being warmed by the sun in spots. I stopped to pull an old gent in a Honda Accord back onto the highway. As i drove off I noticed the park brake warning lamp and ABS warning lamp were both on. I verified that the parking brake was not on or dragging (drums in rear were cold) 10 miles down the road. When I got home I put the truck in my heated garage. Ten minute later both warnings were clear. I suspect a sensor got wet/frozen etc.