If your ESC was manually deactivated, there is a button on your car that you can use to reactivate it. If you are not sure where this button is located on your vehicle, consult your owner's manual. Of course, if the ESC light comes on, you can continue to drive your car. Popular opinion holds that ESC is just another babysitter, something that ruins the fun of driving.
However, for most people, it could save their life. I can speak from some experience here, having spent a bit of time in the left seat instructing on race tracks with "ESC all off on public roads enthusiasts". However, if you can only get the sharpest throttle response and other modes by putting the ESC in sport mode, and you find those modes to be useful, then use the sport modes. Time and time again I have seen them enter a corner too fast, brake and steer at the same time, overwhelm the front tyres and mess up the balance of the car to the point where the ESC light flashed like a Morse code device in the hands of Eddie Van Halen.
Over the course of a few years he got to the point where he could drive very powerful cars very close to their limit. For reference, the average rookie track rat is 30 seconds per lap or more off the pace, and the average advanced black group driver with 50 weekends under his belt is three to five seconds off the pace. I don't plan to do a lot of driver training this year, so maybe I'll add 15 or 20 names to that list. Individual brake calipers can be activated to correct oversteer or understeer, engine power can be modulated and other measures can be taken to help the driver maintain control.
The fact is that ESC helps prevent crashes - reducing light vehicle deaths by 6%, according to the Government - so disabling it is as silly as driving without seat belts, or disabling airbags. Electronic Stability Control (ESC) came about as a result of the advancement of anti-lock braking systems (ABS) over the years. If you notice your DSP, ESP or ESC light coming on, it's a good idea to have it checked by a qualified mechanic. Let's call them the three horsemen of the early track day apocalypse, as many BMW M or Corvette drivers have experienced.
I don't keep track of this figure as obsessively as I do the total number of races or different circuits I've driven, but after doing a late-night spreadsheet, I'm reasonably sure I've trained over 500 first-time drivers on some kind of circuit. When I pressed him on the circumstances, he admitted that he had turned the ESC off to save half a second of his lap time. My view is that if ESC sport mode only affects ESC, then it is generally not worth using it, as sports cars tend to have slightly more permissive ESC than the non-sport equivalent. Systems such as traction control and anti-lock brakes help us maintain control during acceleration and braking, but ESC is designed to prevent loss of control in other circumstances.
THERE IS A HUGE BODY OF RESEARCH that shows that airbags, seat belts and ESC are three of the most important safety features in modern cars.