The check engine light came on one day and would not go off. I had two different mechanics check it and could not find any codes, and could not reset the computer so the light would go out, but could not get it to reset. Now every time the car is running, the check engine light stays on. What can I do to find the problem. Someone told me that there might be a toggle switch under the dash that would shut it off, but where is it located if it is there.