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Interpreting Check Engine Light Warnings

The Check Engine Light, which is also known as a Malfunction Indicator Lamp (MIL), is used as an early detection system in a vehicle to signal the driver that there is something wrong with the engine management system.

This indicator signal is normally positioned in the instrument panel of the vehicle in order to make it visually available to the driver in case it turns on. Usually when it turns on it takes on an amber color to attract attention.

It is equally important to understand that the installation of the Check Engine Light is not the same for all vehicles. For those that are based on the OBD-II (On-Board Diagnostic system) it makes use of a two-stage indicator: steady (for minor faults) and flashing (to signal severe problems).
(Click here to read more about What a Blinking Check Engine Light Means)

The fault code that is associated with a particular problem is stored in the engine control unit so that it can be used to diagnose the cause of the problem to come to an accurate solution.

Skip to:Common Check Engine Indicators|The OBD Check Engine Light System
What You Should Do When the Check Engine Light Turns On
How NOT to React to a Check Engine Light Indicator

The History of the Check Engine Light

The Check Engine Light or MIL (Malfunction Indicator Lamp) made its initial appearance in vehicles during the early part of the 1980s—coinciding with the introduction of computerized engine controls. This was a time when extensive computerization was taking place in virtually all sectors of society, including business and automotive manufacturing. The introduction of the Check Engine Light was part of the self-diagnosis function of the computer controlled engine system.

Initial versions of the MIL were fairly simple and straightforward. When a fault was detected by the engine computer, the MIL indicator on the instrument panel turned on.

Later, the introduction of the OBD-II (On-Board Diagnostic) system added signaling codes to the Check Engine Light. Similar to the Morse code system, the OBD-II system uses different flashes for every code and malfunction.

Common Check Engine Indicators

As part of the electronic control system of the vehicle, the indicator turns on every time it thinks it finds something wrong with the operation of the vehicle. Common MIL (Malfunction Indicator Lamp) indicators included service engine soon, check engine, or check powertrain.

Sometimes the Check Engine Light indicator showed just a picture of an engine which represents the International Check Engine Symbol. In some vehicles only the work check is displayed on the instrument panel.

It is important to understand that the Check Engine Light indicator is just an outward manifestation of a trouble code that represents the specific problem of the vehicle. An electronic scan tool or a diagnostic computer is used to retrieve the code that has been stored. Therefore, to correctly identify the meaning of the Check Engine Light indicators, the services of a qualified mechanic or electrician would be required.

The OBD Check Engine Light System

The original intention for the OBD (On-Board Diagnostic) system was to assist technicians to specifically pinpoint automotive malfunctions to simplify troubleshooting. The system was reserved primarily for the problems associated with the powertrain which can cause a significant impact on the emission system. The OBD system troubleshoots problems based on the specific model, make, and year of the vehicle making their capabilities widely varied.

By 1996 the OBD-II was introduced based on regulations imposed on car manufacturers. This standardized the Check Engine Light system using a more sophisticated method that functions as a built-in emission testing station. It monitors as well as adjusts various functions and components like the fuel system and exhaust system among others.

When a problem is identified it allows self-correction before alerting the driver of a problem. More modern OBD systems have become so efficient that they are checked for trouble codes instead of using traditional tailpipe emission testing procedures.

What You Should Do When the Check Engine Light Turns On

Despite the seeming usefulness of the MIL (Malfunction Indicator Lamp) system, it is a pity that many drivers are unaware of exactly what the light is attempting to say, therefore they do not know how to react. Some car manufacturers have even referred to the Check Engine Light as the most misunderstood indicator on the instrument panel of the vehicle primarily because it can reflect a variety of problems from a loose gas cap to a comparatively serious misfiring engine condition.

According to the National Institute for Automotive Service Excellence, when the Check Engine Light indicator turns on, the driver does not necessarily have to pull over immediately to the side of the road. It also does not mean that a tow truck needs to be called and discontinue the use of the vehicle. What the Check Engine Light indicator means is that the vehicle should be checked out as soon as possible by a qualified automotive technician or mechanic.

***HOWEVER, if your Check Engine Light is blinking or flashing, you should immediately pull over to the side of the road. (Click here to read more about What a Blinking Check Engine Light Means)

How NOT to React to a Check Engine Light Indicator

Without a question only a qualified automotive technician or mechanic will know what is exactly wrong with the vehicle as well as how to resolve it. As a result, it is very important that drivers understand what NOT to do if the Check Engine Light turns on.

  1. Never ignore the indicator warning because it may result in completely damaging expensive vehicle components.
  2. Do not attempt to do a self-diagnosis. While conditions can trigger the Check Engine Light, it does not necessarily mean that you can conclusively know the cause without the proper tools and training.
  3. If you are not a qualified automotive technician or mechanic never attempt to troubleshoot Check Engine Light associated problems, even if you have a tool that can read the stored codes.

Undoubtedly, a vehicle represents one of the most expensive investments that any person can have. Therefore, it is important to value it by giving it adequate attention and care. A Check Engine Light problem is not something that should be left to chance because it can represent a deeper and bigger automotive problem that can permanently ruin your vehicle.

Additional Resources for the Check Engine Light: