Check Engine Light, General Manager of Your Car
By: Grant W. RepsherCheck Engine: What it means
An easy fix
When to head to the shopThe Check Engine or Service Engine light on modern vehicles has taken on several different responsibilities to become a bit of a catch-all in automotive service. Like the general manager of a company, the check engine light can diagnose many potential problems. But it typically see only a handful, and some with rather boring regularity.
A general manager usually sits at the top of an organization, or at least of several different departments, which in the automotive sense includes the emissions system, power train, and engine management (fuel injection). Now, in the case of an international or otherwise "exotic" application, the check engine light's job description may also include overseeing additional "offices," like tire-pressure monitoring, fancy suspension systems, or even complex electronics.
What do these additional items have to do with the engine specifically, you might ask? Well, in many cases nothing. But listing all possible sources of inefficient operation on the dashboard makes no more sense than listing them all on the front of a business card. And because the buck stops with the general manager, it's Check Engine to represent all of them.
Modern vehicles started employing electronics on a wide scale beginning in the 1970s with the 1977 Clean Air Act, but it wasn't until the 1980s (and the first self -adjusting engine in 1981) that the practice become regulated and what's now considered standard. With an oil embargo and fuel efficiency issues still fresh in mind and the new question of automotive-related pollution at the forefront, the idea of onboard diagnostics (OBD) was ripe, and technology allowed for items like engine speed, ignition timing, fuel mixture and eventually emissions, to be monitored "in-house."
The light means that your car is experiencing at least one of the three following issues (in order here of general relevancy and frequency):
· Interruption or fault within the function of the emissions system
· A preset (by time and/or mileage) indication the car is due for general service
· Problem(s) with a component or components that considerably affect the efficient operation or safety of the vehicleEmissions System
The emissions system on your vehicle is actually one of the more complex and extensive of the dozen or so systems hidden in there, and encompasses little understood items like exhaust gas recirculation valve (EGR); the positive crankcase ventilation system (PCV); the air pump; charcoal canister; catalytic converter; oxygen sensor; and muffler, just to name a few.
Supporting this cast is a virtual "sensor city" of little devices tucked in all corners that continually send information back to the car's main Engine Control Unit (ECU). So you can see just by simple numbers there are dozens of parts here that must work in unison, and with different fuel grades, operating conditions, and levels of maintenance, any failure along the line that can't be auto-addressed by the computer can trip the light.
The free spirit that was the '60s unfortunately extended to the design of automotive components, including the gas cap. Before 1970 the cap was vented, actually allowing for the escape of fuel vapors, which were cause for combustible concern. Without a gas cap, the average vehicle can lead to the evaporation of some 30 gallons of fuel into the atmosphere, and the refueling process continues to be one of the more polluting in the automotive industry.
As such strict regulation of gas cap design was instituted, and is now considered an integral part of the emissions system. A faulty, broken, or un-tightened gas cap is one of the more common causes of check engine lights and is certainly one of the very first places to check before scheduling an appointment with your service center.
General Service
While some manufacturers use a mileage and time scale as a way to construct their recommended service and maintenance intervals, others use a more complex system built into the computer's ECU to track the number of starts and stops; length and duration of the average drive; calendar; and other operating inputs to tailor the service or oil change interval to the car's specific driving patterns.
Some of these behavioral systems have an actual indicator describing when service is due, for example with a readout indicating declining mileage (to next service), or by using different colored lights. Some brands and models, however, figure they already have someone employed to do this type of thing. So rather than clutter the already-cramped dashboard, they will simply use the Check Engine light to let us know.
Miscellaneous Component Failure
There are probably 10 additional systems in your vehicle made of hundreds of components just waiting for someone to step out of line so they can "tell the boss" (yup, that general manager again). Rather than try to describe all scenarios, two examples should do the trick.
Your brakes involve a system of parts integral to the safe and efficient operation of your car. The problem is, brakes are in constant use, and because their fundamental design uses the friction caused by rubbing several pieces of metal together as a way to slow you down, brake parts wear out over time.
In earlier cars, there was no indicator to let you know when your brakes required service or replacement. The idea, apparently, was that the trash cans or bumper of the car you ran into when they failed would suffice. As technology and ingenuity progressed, brake pads were designed with a layer that can actually squeal or crunch as you apply the brakes, providing an audible clue as to the state of their not-so-well being. Finally, the most modern cars have changed senses one more time and decided to spell it out visually for those of us who don't get it. You guessed it: the Check Engine Light. (To be fair, some brands do have specific brake system indicators, and brakes represent one of the least frequent trips of the light)
Another example of a component failure, which would be significant enough to set off the light but not related specifically to emissions or safety, is the transmission. Once know simply as the gearbox, the transmission is even more closely related to the engine these days with its own computer control, bank of sensors, and complexity. Any hiccup along the line here could also bring on the light.
With so many potential problems and only one person (or light) to call the shots, how does the general manager keep it all organized? In 1996, all vehicles began utilizing what is known as the OBD II system and a series of fault codes to help diagnose car trouble. A scanning tool is connected to the vehicle (usually near the driver footwell) to a standard OBD port, which can then read the fault codes from the car's ECU. There are dozens of standard fault codes, but some manufacturers also use their own proprietary codes.
The OBD system is essentially the mechanic's translator - to a point. The codes don't describe exactly what needs attention, just that something does, so it's up to the mechanic to connect the dots.
More often than not, the check engine light is really on for minor reasons including, but certainly not limited to, general maintenance or a minor service item. It can, however, be the first sign of something considerably larger. While the easiest DIY fix is to check the gas cap (in the absence of any other symptoms), if that doesn't take care of it after a few restarts, then it is time for a trip to the corner office, or in this case, the garage.
Grant W. Repsher is the founder of Servassist Online. He is a writer with Automotive News, the auto industry's premier trade publication, and a former contributing editor with the AIADA (American International Automobile Dealers Association). To contact Grant about this article or to suggest future topics, please click here.
Copyright © 2005-2007 Servassist Online - All rights reserved