My huge blog on tune up
A steadily illuminated check engine light indicates a non emergency that should be checked out as soon as possible. However, do not ever take your car to an auto parts store to have your check engine light checked out. Auto parts employees are qualified only to interpret the trouble codes, not to diagnose and repair. For service done right, see your certified technician. Minor issues like a loose gas cap, bad spark plug wires or moisture in the engine can trigger a check engine light.