So this has happened to me twice. I drivin my car at very low speeds, engine doesn't exceed the 4th gear for very long distances. I've notice when I drive like this for very long periods of time, my check engine light comes on. Once I drive normal(driving at higher speeds) after a while the lights turns back off. Why is this?? I'm very concerned and I don't want to have a problem down the road.

 

get a scanner, and pull the code...your higher speed is probably completing the drive cycle, and resetting the monitor...but if it throws a code, the ECU should store it.