Virtually all domestic and imported vehicles built in the last 20 years have a Check Engine light on the dashboard. While it’s normal for this (and other) dashboard lights to illuminate for a second or two as you are starting the engine, it is not normal for the light to illuminate as you are driving.
The Check Engine light is part of your vehicle’s onboard diagnostics (OBD) system. Computers have control and monitor vehicle performance, regulating such variables as engine speed (RPM), fuel mixture, and ignition timing, and may even tell the automatic transmission when to shift.
First, 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.
Don’t confuse the Check Engine light with the maintenance reminder or service interval light. These lights illuminate when a routine service is due. They are usually triggered by mileage, amount of fuel consumed, or some other type of vehicle-use measurement.