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A Handy Guide To Your Car's Check Engine Lights

Check engine light


It's an occurrence that can strike fear in even the most experienced drivers; it can conjure images of expensive mechanic bills and vehicles stranded in the middle of the open desert; it's the dreaded check engine light flashing behind your steering wheel.

While it might trigger immediate panic, the truth is that the check engine light can often pop up for minor problems that can be a quick and easy fix. It can also signify a larger issue, however, so you should look into it as quickly as possible.

Before you panic and begin shopping for a new vehicle, here's a quick overview of the five most common reasons your check engine light has been activated.


What the Check Engine Light Means

The Check Engine Light, AKA Service Engine Soon Light, is a signal sign on the dashboard that indicates issues detected in the vehicle. It’s part of the vehicle’s Self Diagnostic function and a signal that a problem is detected by the vehicle computer.

The vehicle has an innate self-diagnostic system and does checks every now and then. When the Powertrain Control Module detects problems, it will record a Diagnostic Trouble Code/check engine light code in the system and ignite the check engine light/service engine soon light when the issue is confirmed.

It’s frustrating to see the blinking check engine light as it does not tell you anything more than “Hey, I got a problem!”. It could be a minor problem that could be solved by simple DIY fixes, or a major issue that brings great danger to your driving. In the next part, we will introduce methods to know what problems lie below the check engine light. It could be identified from the check engine light code.


How to know what happened?

There’s no need to panic when you see the check engine light flashing. If you feel something is completely off and affects your driving, slow down, pull over and call for assistance.

If you don’t feel anything but see a check engine light, basically you can keep driving, as it might be a minor issue. However, make sure you check your car as soon as possible to prevent minor issues from becoming major problems.

You can either take the car to a mechanic for a thorough inspection or check the car by yourself. A diagnostic tool is needed if you want to do a diagnostic test by yourself: OBD2 Scanner, also known as car code reader, AKA engine code reader.

With the OBD2 Scanner, you can read the diagnostic trouble codes/ check engine light code from the vehicle computer, and have a list of codes that indicates where the problems may come from. It doesn’t tell you what the problem is specifically, but you can search for the meaning and possible causes of the trouble codes and follow the instructions. 

For your convenience, we built a website of all diagnostic trouble codes and their explanations, including possible symptoms, possible causes and sometimes with detailed step-by-step diagnostic methods and simple fixes. If you have a list of codes, search here for more information.

After knowing the problem, fixes will be applied to the vehicle. There are several most common fixes and we list them below. Some of them are easy and simple fixes, and some of them require professional mechanics and a high cost.


Oxygen sensor

What it means: Over time, your vehicle's oxygen sensor can become dirty and covered in oil. A dirty oxygen sensor won't prevent your vehicle from running, but it can lower your gas mileage and cause you to fail an emissions test. It can also lead to a broken catalytic converter, which will cost way more than an O2 sensor replacement.

You can learn more about the Oxygen Sensor from this blog. It covers what is O2 sensor and when to replace it.

What you should do: You can either ask a mechanic to replace your O2 sensor, or you can follow the instructions in your owner's manual and do it yourself. Expect it to cost anywhere between $50 and $300.


Gas cap

What it means: If your check engine light comes on shortly after you've filled up on gas, your gas cap could be loose or broken. Because the gas cap helps maintain the fuel system's correct pressure, a dysfunctional one can throw off everything. You could end up losing fuel and increasing your emissions output.

What you should do: Ensure the gas cap is on and tightened. If that doesn't work, you can purchase a new gas cap for under $20 at most auto parts stores.


Catalytic converter

What it means: The catalytic converter is a crucial part of ensuring your vehicle isn't emitting harmful toxins by converting carbon monoxide into carbon dioxide. Over time, it can become dirty and clogged and often breaks if other parts of the engine aren't well maintained.

What you should do: If you notice unusual noise, an inability to increase speed, cloudy exhaust smoke or a decrease in gas mileage, you should visit a mechanic to replace the catalytic converter. Expect to pay between $1,000 and $2,000.


Spark plugs and ignition coils

What it means: Spark plugs and ignition coils are what help a vehicle start and accelerate. If the vehicle is properly maintained, it should only need to be replaced every 100,000 miles or so. But be warned, waiting too long could result in damage to the catalytic converters and other expensive engine parts.

checking engine spark plugs

What you should do: Have your mechanic check these regularly. Replacement for a single spark plug can cost around $20 and a new ignition coil can cost about $50.


Mass airflow sensor (MAF)

What it means: Your mass airflow sensor measure the amount of air enters the engine and adjusts as necessary when you change altitude. A broken one will increase emissions, cause the car to stall, and decrease gas mileage.

What you should do: Keep your MAF safe and long-lasting by regularly replacing your air filter. If it's time to replace the MAF, use your owner's manual or ask a mechanic to install a new one, which should cost around $200.

Buy Tire Safety Monitor 〉

One of the best ways to keep an eye on your car and it's internal components is to use a car health monitor and tire pressure monitor, which can keep tabs on your engine health and tires with real-time alerts and decode engine error codes, which can cause an expensive diagnostic trip to the mechanic.

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