Ok i have a 94 z28 and the ses comes on after about 15 minutes of driving and stays on for about 5 mins then goes away. It seems to be happening everytime i drive the car after 15 minutes. My question is will the code still show up after the light shuts off when you scan. It would be hard to catch it and go and get it scaned before the light shuts off again.

Any ideas of what might be causing this without getting it scaned. Doesnt seem to run any differntly at all with it on or off just the fans turn on??

 

Yes, any code will be stored, even if the light goes off. It will self-clear after about 50 drive cycles without the same problem happening again, but it sounds like your problem is recurring.

 

You asked for a guess and here is mine. I have a similar problem where the SES comes on and then goes away. It is the EGR on my car that is causing this to occur. Usually it happens when I get stuck behind someone driving slow enough to cause me to be between gears. Too slow for third and too fast for second. Once I get out from behind them and open up, the light generally goes away.