I have a 2006 Chevy Cobalt and today as I was driving, my ETS warning light came on and stayed on for about 10 miles. Then I stopped at a store, turned the engine off, went in and stayed for about 15 minutes and when I returned the ETS warning light went off. I then went on for about 30 miles and the ETS light came on again. Oh, and while it was on,the car felt like it was pulling or wanting to slip out of gear or something like it, but only when I slowed down and then speeded up again. What caused this and is it something serious that I need to have checked out immediately? No other lights came on, just the ETS warning light.