Why Did My Check Engine Light Come On and What Should I Do?

When your engine light comes on what do you do? If you said, “turn up the radio” and keep driving, you’re not alone.

Many people ignore dashboard warning lights until either the car starts malfunctioning or it stops in the middle of the road. Have you ever asked anyone why did my check engine light come on?

Instead of ignoring the light, keep reading to learn more. We’ll go over the most common reasons the check engine light on a car turns on and what you can do about it.

Know Your Codes

Wouldn’t it be easy if the engine light meant one thing and one thing only? The reality is there are many things that could trigger the check engine light and isolating the problem usually takes a bit of research.

Depending on the age of your car, you can get identify error codes from the light itself, or you can hook the car up to an error code reader.

Buying an inexpensive error code reader does help you avoid taking the car to a mechanic. Pulling the codes gives you precise information about what you need to do next to address the reason why the light came on in the first place.

If you’re not into checking codes, you can always start with something easier—your gas cap.

Check Your Gas Cap

The easiest step you can take when isolating the cause of a check engine light coming on is to check your gas cap.

No mechanic needed and you don’t need any expensive tools or code readers. You don’t even need instructions.

Here’s what you do:

  • Take the cap off.
  • Put the cap back on.
  • Drive a few times.

This should reset your Onboard Diagnostic (OBD) system and make the light turn off.

If you’re not successful, you may need to replace the gas cap. Buy a cap specifically designed for your make and model. Drive the car a few times and see if the OBD resets.

Congratulations if replacing the gap works! If not, continue reading for more reasons why the light comes on. Also, since you’re into reading, consider buying the manual for your vehicle—having a comprehensive book that covers your car’s various systems is a lifesaver (can save you money too).

You Have a Bad Oxygen Sensor

To run efficiently, your car needs oxygen. Actually, it’s the engine that needs oxygen and it also needs a specific ratio of oxygen to fuel.

Not enough oxygen and the engine runs rich. When the engine runs rich it means there’s too much fuel left over after combustion. When the engine gets too much oxygen, you end up with poor performance and the potential for serious damage to your engine.

The car’s oxygen sensor and engine computer work together to figure out the ratio of oxygen to fuel. Part of this partnership includes adjusting when the ratio isn’t correct. If the oxygen sensor goes bad, the engine’s computer can’t make the adjustment.

Ignoring a faulty sensor isn’t a good idea. In addition to a loss of engine power, you risk corrupting both your spark plugs and the catalytic converter. Speaking of spark plugs, when was your last tune-up?

When Was Your Last Tune-Up?

Regular maintenance, including tune-ups, goes a long way toward preventing major car problems.

Spark plugs and wires are wear-and-tear parts you or your mechanic should change during a tune-up. When worn out, both cause issues with the combustion process. Worn spark plugs misfire and can cause your car to jolt when you accelerate.

If you haven’t had a tune-up recently, don’t wait. Wear-and-tear parts like spark plugs and wires only get more worn out over time, until eventually, they don’t work at all.

A Faulty Mass Airflow Sensor is Faulty

We just talked about the oxygen sensor, but your vehicle also uses a mass airflow sensor to measure how much air you have moving through the air filter. Why should it matter?

check engine lightRemember the oxygen to fuel ratio mentioned earlier? The mass airflow sensor talks to the engine’s computer and lets it know how much fuel the engine needs based on how much air enters the engine.

A faulty mass airflow sensor affects gas mileage. Ignore it long enough and your engine might start stalling out on you. Delay replacing the faulty sensor and you could end up with damaged spark plugs or oxygen sensors.

You also risk damaging the catalytic converter. We’ll cover the catalytic converter next.

The Catalytic Converter

Remember, the engine light isn’t the problem, it’s the warning that something isn’t right. If you have a bad catalytic converter, your engine light may come on as a warning.

The catalytic converter, part of the emissions system, reduces pollution and emissions. It does this by converting the emissions from your vehicle into harmless gasses. Without it, you could suffer the effects of breathing carbon monoxide.

Not sure your vehicle has a catalytic converter? Trust us, if you drive a late model car and it runs on gasoline, you have one.

One of the best things you can do to prevent problems with a catalytic converter is to get regular oil changes. Also, if you don’t take long road trips, take a spin on the highway here and there. It will help prevent your catalytic converter from clogging up.

Are You Still Asking Why Did My Check Engine Light Come On?

We’ve shared a few of the most common reasons for a check engine to trigger.

If you’ve tried our solutions and still can’t get the light to turn off, your vehicle manual should hold some clues. Manuals work great for answering questions like why did my check engine light come on? and they usually offer solutions as well.

If you don’t own the manual for your vehicle, you’re in the right place! Get a downloadable manual here on our site. You’ll find a manual for just about every vehicle known to man.