If you remember any of the codes we could totally diagnose what happened. Since you were passing another car, I'm guessing that you were on the gas, so it could have been some kind of oxygen sensor code. I know that my VX will throw codes when I have extremes in elevation gain (like going over mountain passes). I know the VX always throws codes everytime I do Fins and Things out in Moab. The trail has long climbs and descents and usually the first fin that I go up, during the long climb, the CEL will come on and it is usually some kind of oxygen sensor code.