(AKA - CHECK ENGINE LIGHT)
This lamp illuminates when the vehicles computer detects a problem with the computer controlled electronic devises on your vehicle. These devices in the newer (96 and up) vehicles control far more than just the engine. If all vehicle manufacturer’s placed a warning lamp for all the different functions the vehicles computer controlled, there would not be enough room on the dash for them all.
When the lamp has illuminated, there is a problem detected. What the exact problem is needs to be diagnosed before further damage to a particular control system is incurred. The complication here is that it has to be diagnosed using a ‘scanner,’ that can read the data flow from the vehicles computer. As technology progresses, these scanners are becoming much more complicated to use, but at the same time, give much more information about the operating parameters of the vehicle when they are recording the data-stream trouble codes (verifying the failure the computer has detected, turning on the service/malfunction lamp).
In most cases the lamp illuminates to bring to your attention the fact it has detected a problem and needs attention. The computer will turn on the lamp and substitute a programmed base value (default value) for the failed component, and the vehicle will continue to run. When the computer has substituted a default value the vehicle is in ‘limp mode.’ Overall performance and fuel economy are affected along with cold starting, warm up time, A/C operation, etc., (in most vehicles).
When the engine lamp is on, sometimes it will go off all by itself. THIS DOES NOT MEAN THE VEHICLE FIXED ITSELF. Service is still necessary to find the reason for illumination in the first place. The computer has stored the trouble code in its memory and has sampled the component values again. If they are within the operating parameters, it will use the ‘live’ readings instead of the default values, turning off the lamp TEMPORARALY. - HOW LONG THIS WILL LAST? - NO ONE KNOWS.
Not all trouble codes are the result of a component failure. It may be working within its normal operating parameters and reading right. Other problems may have triggered the out of spec. readings from the component, such as a vacuum leak, bad spark plug, loose gas cap, etc. Computer scanning the vehicle is the only way to determine the problem area and required repair without guessing.
© By Wesley J. Harrison