Five Common Reasons Your Check Engine Light Comes On

When a vehicle’s check engine light turns on, drivers usually have one of two reactions. Some drivers will immediately panic, believing that a huge repair bill is in their future. Others consider it no big deal and will choose to ignore it for as long as possible.

If your check engine light comes on, and you don’t hear any strange sounds, and your car is still driving normally, it probably isn’t an emergency. However, you still need to get it checked out as soon as possible.

Until you can get your vehicle to a mechanic, you may wonder what caused the check engine light to come on in the first place. What follows is a list of some of the most common reasons:

  • 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 is broken, this could cause the check engine light to come on.
  • Oxygen Sensor Failure: An oxygen sensor is a critical component of the emissions system and measures the amount of unburned oxygen in the exhaust system. If you’re experiencing a decline in fuel economy and your check engine light appears, this could be the problem. 
  • Failing Catalytic Converter: The catalytic converter converts harmful emissions from your vehicle into less harmful ones, like carbon dioxide. When your catalytic converter is failing, it’s usually related to other systems that work interdependently with it, for example, spark plugs or the oxygen sensor.
  • Trouble with the Mass Air Flow Sensor: The mass airflow sensor measures the amount of air entering the engine and determines how much fuel is required to run your engine efficiently. A problem with the mass air flow sensor will activate the check engine light.
  • Damaged Spark Plugs or Wires: Spark plug wires deliver the spark from the ignition coil to the spark plugs. If spark plugs aren’t working correctly the air-fuel mixture in the combustion chamber won’t ignite.

These are the most common reasons for the check engine light to come on, but there are many others. Remember, the check engine light isn’t a maintenance check-up reminder. While it is true that it may indicate an easily remedied issue, it also could mean that you have waited too long for maintenance and could be facing a complicated – and expensive – repair.