What Is the Check Engine Light

By Brian Klaubert

You are driving 300 miles to Grandma’s house for a traditional turkey dinner. Half way there your “Check Engine” light comes on.  What should you do?  Most people are uncertain what to do when that little orange light comes on.  How serious is it?  Should I immediately pull over to the side of the road and shut off the engine, or, can I ignore it and drive another 20,000 miles?

The good news is that there is rarely any serious damage potential when the “Check Engine” light comes on.  This light is the alarm bell for your car’s complex computer control system.  Your car has over 50 sensors, and monitors hundreds more system performance indicators for the ignition system, fuel system, transmission, cooling system, and other systems.  The computer has allowable limits for all of these readings and systems.  When a reading exceeds the limit, the light comes on.  The vehicle will be either outside of optimum emissions performance, have deteriorated fuel economy, or sometimes may perform poorly. This light does not just come on at a certain mileage interval to get you to go back to the dealer.

An important tip to keep in mind is that the warning lights on the dash are color coded by priority. An orange light is a warning that some system is not functioning correctly. It generally indicates that a supplemental system is not working. Such systems can include the emissions control system, the anti-lock braking system, the traction control system, or the air bag system.

When these systems malfunction the computer and the system “fails safe”. That is the faulty system will not come on at all. You do not have to worry that your air bag will pop out while driving or that your brakes won’t work. In the instance of an anti lock brake light, your brakes will work just like a car from 10 years ago. They just won’t do that special thing they do when one or more wheels begin to skid.

Each of these systems provides additional safety for you, your passengers, and the other cars around you. So you should not permanently ignore them. You just don’t have to cancel your trip and get a hotel.

A red light is a much more serious problem. A red light means you are about to break down. The two most important red lights are the oil pressure light and the engine temperature light.  If either of these lights come on you should find the first safe place to pull off of the road and then shut off the engine.  Call your repair shop and have the vehicle towed in.  Even a few minutes of operation with either the oil pressure light or engine temperature light illuminated can result in a repair bill beginning at $600 and easily going to several thousand dollars.

There is one red light that is difficult to give advice about. This is the red brake warning light. This light could mean that your brakes won’t work. This would obviously be a serious problem. Unfortunately, this light can also simply mean that you left your parking brake engaged or your brake fluid level has gotten just a little low. I will only report that most vehicle owner’s manuals will advise you to have your car professionally serviced immediately.

Brian Klaubert owns Christian Brothers Automotive – Hamilton Mill, on Hwy 124 in Dacula.