Re: SES only goes off by itself when. . .
Mike is right. You really need the service tech to read the codes. I had my SES light go on and off a couple of times in the past. One fault was a misfire in cylinder 5. The other times were from my post cat O2 sensors. I ended up having to replace both those sensors. The misfire event reset itself (SES light went out) after stopping and re-starting the car. The O2 sensor faults kept the SES light on until the service tech reset it