Why is my Check Engine Light on?


Seeing a car’s check engine light illuminated on the dashboard can create a sense of dread for drivers who equate the symbol with expensive repairs. The light indicates a malfunction in one of the vehicle’s systems, but even minor issues can trigger an alert.

If your check engine light is flashing, there is a serious problem and you should turn off the engine as soon as it is safe to pull off the road. After stopping your car, you’ll want to know why your check engine light is on in the first place and how to fix it.

What Causes a Check Engine Light to Come On

Modern cars have a check engine light to let the driver know something is not working as it should. Known technically as a Malfunction Indicator Light (MIL), this warning light on your dashboard is shaped like a car engine. The light may be amber, red or yellow, depending on your vehicle. Some models display “check engine” with engine outline.

Sensors monitor the many complex functions of your engine. The car’s system receives information from sensors to self-diagnose internal problems. Automakers use the second generation of standardized on-board diagnostics, known as OBD-II, for model years 1996 and later. Older cars use an earlier iteration of the OBD protocol.

If the sensors detect information that is outside of a normal range, the system creates an OBD-II code, which activates the warning light.

  • Check the engine light on: When the check engine light comes on and stays on, the problem is usually with the emission systems or some safety-related fault.
  • Check that the engine light is flashing: A blinking or blinking check engine light indicates a problem serious enough to damage critical systems such as the catalytic converter, internal engine fuel, or air induction systems.

Do not confuse the check engine light with your car’s maintenance required or service required light. This service notification is shaped like a wrench and alerts you that an oil change or other scheduled maintenance is scheduled.

Diagnosing engine light problems

Your vehicle’s diagnostic trouble codes can be accessed using an OBD-II scanner or reader that connects to a 16-pin port usually located under the steering column. You have three options for obtaining the code that triggered the check engine light.

  • Find an auto repair shop that will use their scanners to diagnose the problem for a fee. Stores generally waive diagnostic fees if you have the corrective service performed there.
  • Go to an auto parts store and have the code scanned for free. If the code indicates a minor issue, you may be able to fix it yourself.
  • Purchase an OBD scanner at your local auto parts store or online. A good quality reader can cost less than $50. Additionally, hundreds of OBD-II apps are available for your smartphone, and the car’s Bluetooth is used to access diagnostic trouble codes. These wireless options are available at all prices, including free. In some cases, you might get what you pay for.

Even if you don’t do the repairs yourself, getting codes is beneficial if you want to double check against what your mechanic said. This helps ensure that the service center is addressing the correct issue with your car.

Check diagnostic trouble codes

Every driver should understand the meaning of the warning lights that signal problems with their vehicles. The owner’s manual will illustrate where the symbols appear on your gauge panel and help you interpret their meaning. Take this information seriously and pay attention to any warning lights that come on.

It’s never a good idea to ignore a check engine light. It is wise to take the car to a mechanic when the light comes on and fix the problem. If you do your own investigation and determine the code that is causing the warning, look for a OBD II code list to tell you which specific component has a problem.

Not all check engine warning lights cause big bills. Sometimes the problem is as simple as tightening the fuel cap. Others, especially when accompanied by oil or temperature warning lights, can mean bigger issues at hand. However, if the oil or temperature warning lights come on, immediately stop the vehicle in a safe location and turn off the engine. A lack of oil or high engine temperature conditions can permanently damage the engine and other components.

Turn off engine warning light

If your state requires an annual vehicle inspection, you will first need to address the problem behind the check engine light. A car will not pass inspection if the check engine light is solid or flashing.

If a mechanic fixes the cause of the check engine warning on your car, they should reset the diagnostic system to clear all codes. Most OBD scanners you can purchase will erase and reset codes that illuminate the check engine light, even if you haven’t fixed the problem. The light will come back on, and ignoring the root cause can create even more problems and greater expense.

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