If the check engine light comes on:
Look for a serious problem that requires immediate attention.
Check your dashboard gauges and lights for indications of low oil pressure or overheating. These conditions mean you should pull over and shut off the engine as soon as you can find a safe place to do so.
Try tightening your gas cap.
This often solves the problem. Keep in mind that it may take several trips before the light resets. Some vehicles have a separate indicator that warns of a loose gas cap before the condition sets off the check engine light.
Reduce speed and load.
If the check engine light is blinking or you notice any serious performance problems, such as a loss of power, reduce your speed and try to reduce the load on the engine. For example, it would be a good idea to stop towing a trailer. Have the car checked as soon as possible to prevent expensive damage.
Have the code read and the problem fixed.
Take the vehicle to a professional. Some automotive parts stores will read and interpret the code for you. However, unless there is an easy solution to the problem, you should have the vehicle diagnosed by a qualified service technician directly tell what's wrong, so you have to test to find the real culprit. This is where the real meaning of codes comes into play. The only thing a code really indicates is which system or circuit to test in order to isolate the actual problem.