Top 5 Reasons Your Check Engine Light is On

check engine light

You’re driving down the road, not a care in the world, and then you notice something — your check engine light has illuminated. While it is important to inspect your vehicle shortly after the check engine light appears, it may not be a reason to panic. There are a number of reasons why it turned on and there are several things you can do to troubleshoot the problem before having it checked by a professional.

When it is convenient and safe for you to evaluate your vehicle, do so. Reasons why your check engine light is on include:

  1. Loose Gas Cap
    This is the first item you should check. The gas cap seals the fuel system ensuring proper pressure is maintained in the gas tank. If your gas cap isn’t on tightly or appears chipped or cracked, this could be the reason your check engine light is on. If it’s just not on properly, secure the cap and re-check your dashboard to see if the light turns off. You may have to turn off and then turn back on your vehicle.
  2. Failing Oxygen Sensor
    If you’re experiencing a decline in fuel economy and your check engine light appears, have your oxygen sensor checked. A professional can check the condition using a diagnostic code reader.

    What is an oxygen sensor?

    An oxygen sensor measures the amount of unburned oxygen in the exhaust system and is vital to the emissions system.
  3. Failing Catalytic Converter
    When your catalytic converter is failing it’s usually because you ignored several other issues. These issues are related to other systems that work interdependently with the catalytic converter (spark plugs and wires, oxygen sensor etc.).

What is a catalytic converter?

A catalytic converter is an exhaust containing a catalyst that converts pollutant gases into less harmful ones, like carbon dioxide.

  1. Failing Mass Air Flow Sensor
    Always have your mass air flow sensor checked when the check engine light comes on. Since many of the parts of the engine work together, when one part fails, others tend to follow suit.

    What is a mass air flow sensor?
    The mass airflow sensor measures the amount of air entering the engine. It determines how much fuel is required to run your engine efficiently.
  2. Damaged Spark Plugs or Wires
    Without properly functioning spark plugs, your vehicle will not start. Spark plugs ignite the air/fuel mixture in the combustion chamber of your vehicle. The spark plug wires deliver the spark from the ignition coil to the spark plugs

It’s important to keep in mind that these are the most common reasons for the check engine light to come on; however, there can be other issues that cause the check engine light to illuminate.

What Happens if I Ignore the Check Engine Light?

First, determine if your check engine light is just illuminated or if it is flashing. A flashing check engine light indicates a major internal failure and requires immediate attention. Regardless, do not ignore the check engine light. Continuing to drive with a non-flashing but illuminated check engine light can result in lower fuel economy and eventually lead to more significant and costly repairs. Many of the systems work together, so a failure with one system can cause a chain reaction in performance with the others. If you were to take in your vehicle for state inspection while your check engine light is on, you will fail the emissions test.

A check engine light should always be checked as soon as possible to ensure the integrity of your vehicle. View the Top Driver maintenance checklist to ensure your vehicle is runs smoothly from your first destination of the week to your last.

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