Over the past few weeks I have fielded inquiries regarding check engine lights and how to reset them.  The light its self is harmless but it does become a nuisance when its on all the time and especially at night when its reflection makes you glow.  The solution is usually not as simple as disconnecting the negative battery terminal or to reset the light with a scan tool.

The check engine light will come on for a number of reasons relating to sensors in the drivetrain or emissions system.  Along with the light, their is actually a code that is produced that can be read by a scan tool that will tell what the issue is.  In some cases, it can be as simple as a loose fuel cap.  It is  in the best interest of the car owner to investigate why the light is on rather than dismissing it as a nuisance.  Interestingly enough, clearing the code with a scan tool does not mean the problem has gone away or the code is permanently removed.  Actually, the light should come back on at some point and the code its self will be stored in the vehicle computer for retrieval at a later time.

My advice is simple, if and when this light comes on be aware that the vehicle computer has diagnosed a fault.  The proper course of action is to have the fault scanned by a qualified mechanic shop or dealer to understand what the risk is to your vehicle.  Ignoring the light, covering it up or resetting it will not make the issue go away so try to have it serviced sooner rather than later.  Although having to spend money to repair the cause of the check engine light may not be pleasant it could be a blessing to have a well performing vehicle when you most need it to perform.