Q: What Types of Trouble Codes Cause Lights to Come On in My Dash?

Different vehicles have a different number of lights on the dashboard to warn you of problems, some with just a few basic lights while others have plenty to distinguish between different issues. This article will cover just the bright yellow light that says Check Engine, Service Engine Soon, or has a symbol of an engine on it. When this light comes on, it is due to a problem with one or more systems in the vehicle. This article will help you better understand the reasons the light comes on.

There is much debate who had the first Check Engine Light (CEL) to alert the driver there is a problem. There were manufacturers that started using them dating back to the late 1960’s but it was not till the year 1996 that there was a group effort by most if not all the manufacturers to standardize what is now called on board diagnostics (OBD). Since then there has been improvements to the systems to both control and monitor the operations of the engine, transmission, and other systems. The CEL does not come on for every fault in these systems but will come on for the most part when the vehicle manufacturer thinks it may harm the occupants or vehicle and is a safety hazard. It will blink or come on when the emission levels are thought to be exceeding limits imposed by the Environmental Protection Agency (EPA).

The codes that will cause the light to come on in the dash are mostly all engine or transmission trouble codes. The manufacturer may allow the light to come on for additional systems and these codes can be OBD generic or manufacturer specific related codes. There are over 3000 possible codes that are used for vehicle systems. Most codes below 1000 are generic type codes and the rest can be generic or manufacturer specific.

When the Check Engine Light comes on the operator should look for common problems like the fuel cap was left off. Open the hood and look for visual loose items like air filter inlet hoses. Your Check Engine Light is only going to alert the operator that there is a problem and a computer scan will give you a diagnostic code that can be diagnosed. The light was designed to alert you to take it to a mechanic to have it tested and diagnosed. Today’s drivers now have their own diagnostic scanners or go to parts stores where they scan your car for free and give you a code so you can search it up and replace the part that may fix the code. This is where the CEL can sometimes lead to a misdiagnosis and hurt the vehicle owner. The code is designed to help direct a mechanic to a specific pinpoint test that will isolate the fault for a correct repair. The repair does not always include replacing parts.

If you have a vehicle that has the Check Engine Light coming on, then remember that the light is letting you know that you have a problem that can do harm to one or more systems in your car or may be unsafe to operate your vehicle. You should get the light diagnosed as soon as possible to prevent being stranded or harming vehicle systems. There are other lights on the dash that may come on at the same time in some vehicles to alert you to a particular system that is having a problem. You may see lights like ABS, airbag, SRS, EPC, TRAC, TRANS, or others that will cause the Check Engine Light to come on if the engine is using that system for its controls. The engine and these other modules communicate on a network in most vehicles and the engine control module (ECM) controls the CEL through this network of modules.

The next time you see the Check Engine Light on, keep in mind the complexity of the systems involved in turning on this light and some of the possibilities and problems for damage to your vehicle systems. If you are unsure where the problem might lie, have a certified mobile mechanic from YourMechanic inspect your Check Engine Light at your home or office.