Check engine light on dashboard.

What causes a check engine light to turn on?

In Automotive Diagnostics by HomeTowne Auto Repair & Tire

During your daily travels or on extended trips, you may have noticed your car’s check engine light turn on.

This symbol isn’t one that should be ignored for long. When it appears on the dashboard, it’s cluing you in that there’s a problem. What that issue is exactly … well, that mystery can take some time to solve. The root cause could span a number of components and various systems.

Every vehicle is made up of a different set of monitors. Some examples include fuel monitors, EVAP monitors, and catalyst monitors.

The car is constantly testing itself, with several tests performed at one time. Each test has a certain parameter, and a code is sent if something is wrong.

Flashing check engine light

Check engine light on Kia Optima.

Before we delve into the possible culprits behind a check engine light, we want to point out that you should avoid driving a vehicle if the icon is blinking.

If you’re driving when this occurs, pull over to a safe location and have it towed to a mechanic or auto repair shop you trust. Continuing to drive the car when the light is blinking can lead to catalytic converter damage.

A lot of times, a flashing check engine light may indicate a large misfire. You could have a bad spark plug or ignition coil. It’s also possible that a fuel injector is failing or the driver inside the computer isn’t sending the signal to that cylinder.

It’s OK to use the car if the light remains solid, but we recommend getting it looked at as soon as possible. Bringing the vehicle in sooner rather than later allows the automotive expert to address any major problems. This also makes it easier for them to figure out the initial code (and helps up the diagnostic testing process).

Check engine light causes

Numerous problems can lie behind a check engine light.

Maybe the spark plugs or ignition coils are going bad, or there’s a malfunctioning sensor. You might have a loose gas cap that needs to be tightened. Being low on oil is another possibility.

Spark plugs.

The could be a sign that the catalytic converter isn’t working right. This was the case with a Dodge Caravan we worked on.

Problems with the circuit system, catalyst system and coolant system are also reasons why the symbol appears.

A misfiring engine is a more serious issue that the icon would point out.

Here are other potential check engine light causes:

  • Problems with the transmission
  • Oxygen sensors
  • Evaporative system issues
  • Anti-lock braking system (ABS) problems
  • Wrong oil

Other symptoms to watch for

If you see the check engine light turn on, make sure to note when it appeared. We also recommend that you keep an eye (or ear) out for other symptoms. 

Does the vehicle feel like it’s running rough? Do you hear any noises? Did any other dashboard lights come on?

The sounds and behaviors you notice can vary. So, just be aware of anything out of the ordinary.

Some of your observations might not seem important. However, sharing these details with an automotive professional can narrow down their search as they track down what’s causing your check engine light problem.

HomeTowne Auto Repair & Tire is an authorized Michelin and BFGoodrich tire dealer located near Lake Ridge, Virginia. Automotive repair services are performed on all makes and models, including oil changes, brakes, alignments, inspections, and computer engine diagnostics.