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What to do if your check engine light comes on

Warning – engine trouble ahead!

A tachometer in a car's dash showing a check engine light illuminated.

Few things can put a damper on your day like seeing the check engine light, also referred to as the MIL (Malfunction Indicator Lamp) or SES (Service Engine Soon) light, illuminated on your dashboard display. You wonder what is going on with your vehicle and how serious it may be.

Before you go into full-fledged panic mode, take a deep breath and try to relax. There are many reasons why your check engine light can come on – some are minor like a loose gas cap, while others are signs of serious engine issues.

While it is tempting to ignore your check engine light, resist the urge – it could cost you down the road. What is an easy issue to fix today could become an expensive repair if you neglect the warning signs. Read on to learn what steps you should take if your check engine light comes on.

Should I keep driving my car?

Side profile of a sedan driving on the road with the scenery in the background blurred to show that the car is moving.

A blinking check engine light usually indicates that there is an issue that needs immediate attention from your service provider while an illuminated check engine light typically signals a problem that isn’t an emergency. However, you should still get your vehicle checked as soon as possible.

While it’s your decision whether to get your vehicle checked out right away or to wait, don’t take the choice lightly. Carefully inspect your vehicle before continuing on your journey. If you hear unusual noises, experience a loss of power or see smoke coming from your engine, these are all signs that there could be a serious problem with your vehicle’s engine. If possible, have your vehicle towed to your local service provider for a thorough inspection. You don’t want to risk doing further damage to your engine by continuing to drive.

If you do decide to continue driving your car, be sure to monitor your vehicle’s performance in the coming days. If you begin to experience engine issues like poor performance or decreased gas mileage, get your car examined by your service provider.

Also, be aware that there could be multiple things that cause the check engine light to come on. There could be other codes that pop up while the light is on. If the light is still on after the initial inspection, then be sure to have your vehicle rescanned to ensure all codes/issues are resolved.

Troubleshooting the check engine light

If your check engine light comes on, there are some things you can do that may fix the issue. If your vehicle has a gas cap, start by making sure if it is on tight. You may be surprised to learn that a loose gas cap can cause your check engine light to come on.

Also make sure the oil dipstick is properly seated and that the oil fill cap (located on top of engine on the valve cover) is on tight. Both of these things can set off the check engine light. Be sure to check all of these before taking your vehicle to the shop or dealership for service.

The light is still on – what should I do?

A mechanic smiling with his arms folded standing in front of the side of a vehicle with its hood up.

At this point, it is time to make an appointment with your service professional. In some cases, an illuminated check engine light is an indicator of more severe problems. There is potentially something serious going on with your vehicle’s engine and you don’t want to wait to get it checked out.

What does the check engine light mean?

There are a variety of things that can trigger your check engine light. Here are some of the more common engine issues:

Oxygen icon.

Oxygen sensor

The oxygen sensor monitors the oxygen level in the exhaust as it leaves the engine and helps maintain an optimal air/fuel mix. A failing sensor can affect your gas mileage.

Catalytic converter icon.

Catalytic converter

The catalytic converter keeps your car environmentally-friendly by changing carbon monoxide into carbon dioxide. Driving with a failing catalytic converter can cause your car to produce harmful emissions.

Spark plug icon.

Spark plugs or ignition components

The spark plugs or other ignition components play a key role in the combustion process. Failing spark plugs or other ignition components can cause you to experience a loss of power, engine misfires and poor gas mileage.

Thermometer icon.


The thermostat helps regulate your car’s temperature. If it malfunctions, your car may run too cool, affecting your fuel economy or it could overheat which can cause further damage to your engine.

Four wavy blue lines on top of eachother icon.

Mass air flow sensor

The mass air flow sensor measures the amount of air coming into the engine. Your car’s computer uses the information to inject the correct amount of gas into each cylinder. Failing to get it fixed can result in rough idling and poor fuel efficiency.

While most codes are emissions or drivability related, many powertrain control modules (PCM) can illuminate the check engine light for other concerns like transmission-related issues. Some codes can be triggered by systems that only work at higher RPMs/loads, so the driver may not notice the issue while driving at normal speeds. But when the vehicle needs to perform at higher speeds, the engine may experience performance issues like not being able to get up to speed or knocking which can cause the check engine light to come on.

What will my service provider do?

Your service provider will start by plugging a code reader or scanner into your vehicle’s OBD-II port. The scan tool gathers diagnostic information from your vehicle and gives a numerical code or multiple codes that can help your service provider diagnose your vehicle’s issue. In addition, most advanced scan tools can give information on multiple engine parameters while the vehicle is running to help your service provider better diagnose the repair and get you back on the road.

The content contained in this article is for informational purposes only and should not be used in lieu of seeking professional advice from a certified technician or mechanic. We encourage you to consult with a certified technician or mechanic if you have specific questions or concerns relating to any of the topics covered herein. Under no circumstances will we be liable for any loss or damage caused by your reliance on any content.

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