I'm guessing it is probably nothing but today I had the ESC light come on and stay illuminated. I stopped, turned the car off, restarted and it went out, I drove about 3 hours home and it's still out.
The circumstances surrounding it were:
I was driving down Mt. Washingtond auto road, it was very steep pavement (average 12% grade, max 22%, estimate 18% where I was at the time), running manually in 1st/2nd gear at about 20mph turning a sharp right right corner, and I might have had sport mode on from earlier. All fluid temps were good. No weird noises, and I don't think a tire slipped over one of the road edges. Ran it for codes, none appeared...Just a sensor which went off accidentally or what do you think?