What's that light on my dash called "check engine"?
Source: Tech-Net
Although it is commonly known as a "check engine light," it actually has more to do with your vehicle's on-board computer system rather than your car's engine. This warning light is also referred to as the engine malfunction light, power loss light, service engine light or service soon light.
As far back as the early 80's car companies have used on-board computers to control and monitor various engine systems. Computers now control fuel, ignition, pollution and other vehicle systems which were once mechanical. The purpose of this technology is to decrease air pollution, maintain good fuel economy and to increase the overall efficiency of the modern automobile. With this technology comes the need to have a system where-by the computer can actually check itself and help in the diagnostic process should a problem occur. For this reason, the "check engine" light was incorporated as part of a warning system on your dashboard.
When the check engine light is on, the vehicle's on-board computer system is telling you that there is a problem. Many times the problem will be minor. The problem may fuel related, electrical, ignition, engine or pollution related. Most problems may be simple in nature but may take sophisticated diagnostic procedures to identify. Don't be fooled by a "free" check engine light diagnosis. With the amount of knowledge and high-tech equipment needed to diagnose a vehicle's on-board computer system it would be in your best interest to pay a trained professional to analyze your problem.
Intermittent glitches can also occur which can turn on the check engine light. These problems can be very difficult to solve and may even require your vehicle's on-board computer to be updated or re-programmed. You should always have a trained automotive technician test your on-board computer when the check engine light comes on, even if you don't experience any obvious problems.