What does my "Check Engine Light" indicate?

How do I Turn Off the Check Engine Light?

This is a common question. The easy answer is to bring your vehicle to us so we can determine what caused it to light up. But, you want and deserve more information than that, so here is a brief explanation of what that annoying little light means.

It all has to do with vehicle emissions and the monitoring of any system that might affect the stuff coming out of your tailpipe or some other part of your car. The check engine light (CEL) is also referred to as the malfunction indicator light (MIL). It is the most obvious part of your car’s On-Board Diagnostics (OBD), a system required on all vehicles since the mid-1990s. Whatever that little light is called, it often causes some anxious moments.

When the light comes on, it means one of your car’s many sensors has detected a problem, causing the car’s computer to store a diagnostic trouble code (DTC). These codes point to specific systems or components that may have triggered the light. The key word here is “may.” For example, if a DTC points to the oxygen sensor, your first reaction might be to replace it. In fact, the root cause may be something else that is only affecting the oxygen sensor, but is also having a negative effect on your fuel economy.

DTCs can be compared to the names of streets on a map. Once you are on the street, you still have to knock on doors to find the specific house you are looking for.

Automotive technicians use scan tools to start them down the path to finding the source of the DTC. The scanner plugs into a port under the dashboard and displays any DTCs stored in your car’s computer. Now at least the technician is “on the street.” More diagnostic testing will help him or her find the right address and fix the problem. Sometimes, the solution is as simple as a loose gas cap.

If your check engine light comes on, but your car is running fine, we urge you to get it checked anyway. You may not detect any damage being done, but ignoring the light could be expensive. For instance, by continuing to drive you may be damaging your catalytic converter – a very costly repair. Even without other obvious symptoms, your car could be using substantially more fuel. Driving with just a 15% reduction in fuel economy could cost you up to $22.00 per month.*

The original question was, “How do I turn off the check engine light?” The answer remains, “Bring your vehicle to us to determine the cause.” At least now you have a better idea why. Once the vehicle is repaired, your technician will “clear” the DTC(s) from the computer and you can be on your way.

Happy driving!

*Based on an average 12,000 miles per year with a calculated fuel cost of $2.50 per gallon and average fuel economy of 20 mpg.