Perhaps the scariest event in a car owner’s life is when the “Check Engine� light comes on. What does it mean? Should I get the car to a repair facility as soon as possible? Is the car safe to drive? Is my engine about to fall apart? That light does not come on randomly for no apparent reason, there is something going on with your car. But most times it is a relatively minor problem and your car is safe to drive until you have the problem fixed.
The Check Engine light is a relatively new development in automobiles; they are a direct result of the use of computers to control the operation of the car’s engine. This light is part of the federally mandated engine control systems that keep modern automobiles clean and efficient. By law the Check Engine light must function properly, if the light bulb burns out or becomes disconnected for some reason your car will not pass any state’s smog inspection. And as an automobile owner, you want the Check Engine light to work.
The basic function of the automobile gasoline engine has not changed since the first Daimler wheezed down a German strasse over one hundred years ago. The engine mixes a bit of gasoline with some air, passes the mixture into a cylinder, ignites that mixture with an electrical spark, the resulting explosion causes the pistons to go up and down with the resulting exhaust passing out of the cylinder. Engines then and today have cylinders, pistons, crankshafts valves and cams. Outside of the increasingly better and stronger materials to make these parts out of, the single greatest difference between your modern chariot and a horseless carriage are the regulatory mechanisms of fuel, air and ignition. In the old days these things were regulated by manual adjustments made by the driver and in later years a series of crudely automated mechanical regulators. Today precise measurements made by computerized systems regulate those functions, plus in the newest cars cam timing is also adjusted by the computer. All that precise computerized regulation allows your engine to be as clean and as powerful as it can be.
Those computerized systems are all interconnected to a single central computer (cleverly hidden in some unexpected spot under the dash typically, check your owner’s manual for your car’s computer location) that balances the car’s engine needs for fuel air and ignition timing based upon atmospheric conditions, grade of gasoline and load on the engine. The central computer receives data from sensors through out the engine system and balances that data input to control the engine. When one of those sensors receives information that is out of strictly defined parameters, the computer gets an alert and in turn ignites the Check Engine light.
So now the Check Engine light is on, now what? If you are a panicked car owner you rush down to you favorite service center and throw yourself at the mercy of the Service Writer. “Oh please sir, interpret this sign and make it go away.� And like Snidely Whiplash collecting on the overdue mortgage payment, the Service Writer will curl his lip into a snear and tell you, “Leave it with us over night and we will see what we can find. There will be a minimum three-hour labor charge at $100 per hour to diagnose the problem. Once the car is diagnosed we will discuss the cost of fixing the problem.�
If you are a smart car owner you will reach into the glove compartment for the owner’s manual. Searching the index under “Check Engine Light� you will turn to the page indicated and read that the car’s central computer has detected a problem and that the car’s computer can tell you what the exact problem is. If you car is of an enlightened design, like Honda, the computer will visually display easily read code numbers that can be checked against a list of codes (usually available in the owner’s manual, but sometimes found in a $10 service manual available at your local auto parts store) that will tell you the owner EXACTLY what the car’s problem is.
Thus armed, you can repair the problem yourself or you can look the Service Writer right in the eye and say, “The Computer is throwing an Oxygen Sensor code. Fix it.� And the Service Writer will be so impressed by your knowledge and strength of conviction that he will forget to try to sell you a transmission flush or a set of engine mounts that you do not need.