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Honda Civic Check Engine Light: Warning Codes & Common Causes

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We’ve scanned over 43,023 Honda Civics with the FIXD OBD2 scanner and app. These are the 5 most common reasons for a check engine light in your Honda Civic.

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5 Most Common Reasons for a Check Engine Light in Your Honda Civic

Learn How To Easily Find The Cause Of Your Problem And Fix It Yourself

Code Severity  Description
P0420 MODERATE– Extended driving with this code can cause internal engine damage Your catalytic converter isn’t functioning efficiently. This could increase the output of harmful pollutants.
P0302 SEVERE – Stop driving immediately Cylinder number two is experiencing misfires, which could cause damage to your engine or emissions system.
P0303 SEVERE – Stop driving immediately Cylinder number three is experiencing misfires, which could cause damage to your engine or emissions system.
P0135 MODERATE– Extended driving with this code can cause internal engine damage A heated oxygen sensor is not heating up properly, causing excessive emissions.
P0300 SEVERE – Stop driving immediately Two or more cylinders are experiencing misfires, which could cause damage to your engine or emissions system.

Other Common Honda Civic Issues

  • Why won’t my engine start?
  • Where is this gas smell coming from?

Why Won’t My Honda Civic Engine Start?

You may encounter a problem where your engine will crank when you turn the key, but it won’t start. There is a known defect with the fuel pumps Honda installed in several models, including the Civic, where they will fail and not pump enough gas to the engine for it to start or run. There is a recall for this problem. If your car is covered under this recall, Honda will repair it for free.

Where Is This Gas Smell Coming From?

Some Civic owners report smelling gas inside the passenger compartment. The engine relies on the heat it generates while running to completely burn all of the gas inside the engine. If you mainly take short drives, though, the engine may not completely warm up, resulting in unburnt fuel inside the engine. This can leak into your oil, causing its level to actually go up. This will even cause the check engine light to turn on if your oil level gets 21 millimeters too high.

The immediate fix for this problem is to change your oil. The gas mixing with the oil is not a lubricant, and reduces the oil’s ability to do its job. Once you have fresh oil, try taking a longer drive from time to time. This will allow the engine to warm up completely and burn off any excess fuel.

Check Your Gas Cap

One of the most common reasons for smelling gas in your Honda Civic, as well as activating the check engine light, is also the easiest problem to fix: a loose gas cap. This happens because the engine detects a leak in the evaporative emissions system, which exists when the gas cap isn’t tightened until it clicks. It’s easy, and it’s free!

What Should I Do If the Check Engine Light Is On in My Honda?

There are many issues that can cause the Honda Civic check engine light or check emission system indicator to turn on, from a loose gas cap to major engine issues. Check out our guide on what to do when your check engine light comes on. Following this guide can help you avoid driving with a serious problem and causing more damage to your engine. 

If you’d like some more information on diagnosing a check engine light yourself, you can also check out our article on the most common reasons for a check engine light.

For those of you who prefer a mechanic, you can find a trusted repair shop for inspection easily with RepairPal.

> Find a RepairPal Certified Shop Near You

What the Check Engine Light Means

Your Civic engine warning light is part of the onboard diagnostics system (OBD2). All gas-powered cars and trucks made since 1996, plus diesel cars and trucks since 2008, have a diagnostic system to manage the engine and monitor system performance. It alerts the driver to any engine problems by activating the Check Engine Light, on your dashboard. The Check Emission System light will turn on for issues specifically related to your exhaust and emissions. Special tools can access diagnostic information from this system to find out what’s wrong with your car and how serious the problem really is.

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How to Read Your Civic’s Check Engine Light

There are a few ways you can read the diagnostic trouble code stored in your car’s computer.

1) Go to your local mechanic. They will plug in their professional OBD2 scan tool to read the code and identify the cause of the problem. They will likely charge you a diagnostic fee for this service. You also may not have a relationship with a shop that you trust to diagnose the problem accurately, rather than try to profit from repairs. It also won’t help you if you’re broken down on the side of the road. 

2) Go to a nearby auto parts store. Most parts stores will plug their OBD2 scanner into your car and give you the code and technical description at no charge. The person providing this service may not be a mechanic, though, and may not be able to provide any more information than what the scanner tells them. It’s also possible that they may try to sell you products you don’t need in order to “fix” the problem.

3) Read your own check engine light codes with or without a scanner. Checking codes manually can be done but, it’s tedious. Borrowing a scanner or buying one makes the process easier. There are many OBD2 scanners you can buy that will read codes and provide other engine information anytime you want. FIXD is able to translate any Honda check engine light or check emission system trouble code into plain English directly on your smartphone. 

How the FIXD Check Engine Scanner Works

The FIXD car scanner plugs into your car’s OBD2 port. This is a trapezoid shaped plug located under the steering wheel. Read more about how to find your OBD2 port on your particular car.

most common locations for OBD2 port in car


The FIXD Sensor and free mobile app explain in plain English what problem codes your car has recorded. You will get a detailed description of the problem so that you can make informed decisions about repairs.

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Get Maintenance Alerts

FIXD can automatically alert you when your Honda Civic is due for an oil change and other routine maintenance, based on your specific model and its mileage.

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Monitor the Health of Your Honda Civic

FIXD will immediately send a notification to your phone if your check engine light turns on. You can also monitor data in real time, such as oxygen sensor voltage, fuel trims, vehicle speed, and more.

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Does FIXD Work with Your Honda Civic?

FIXD is compatible with 1996 or newer gas-powered Honda models, as well as 2008 and newer diesel cars and trucks. Use the Compatibility Checker for additional info.

Is It Safe to Drive with My Check Engine Light On?

That depends on what problem triggered the light to come on in the first place. You will need to use an OBD2 scan tool like the FIXD Sensor to find out the exact nature of the problem, how severe it is, and whether or not it’s safe to keep driving.

If your Check Emission System light is on, it’s generally fine to keep driving. The engine is fine, but since it’s not running as efficiently as it should, you should investigate the problem and have it repaired when you can, especially if you live in a state that performs vehicle inspections.

Generally speaking, if the Check Engine light is a steady yellow light, it should be okay to keep driving. This is usually a minor that doesn’t affect drivability. While your car will keep running just fine, it’s still best to get this diagnosed and repaired soon.

If the light is blinking, you should stop as soon as it’s safe to do so. This indicates a serious problem, such as a misfire, that is occurring right then. It’s also good to check for low oil or overheating. If your Honda Civic’s check engine light is red, you should stop driving immediately.

If your Civic experiences driveability issues, such as reduced power or misfires, slow down and take it easy on the engine to avoid making the problem worse.

How Can I Reset the Check Engine Light in My Civic?

If you have resolved the problem, you may want to clear the codes that triggered your Honda Civic engine light. If you reset the light, drive, and it doesn’t turn back on, your problem is fixed.

The easiest way to reset the check engine light on your Honda Civic is with FIXD. While auto parts stores will typically read your codes for free, they will not reset the light for you, and shops may charge more than $100 to do this. 

In the FIXD app, you can reset the light anytime you want for free. After performing the engine scan, go to the Details page and click the “Clear Engine Light” button. The light will turn off, and any codes stored inside your Civic’s computer will be cleared. If the light turns back on after a few miles of driving, the issue likely still exists.

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Diagnose Your Honda Civic’s Check Engine Light with FIXD

If the check engine light turns back on, use FIXD to get detailed engine diagnostics, plain English code descriptions, issue severity warnings, and so much more. Learn more about the FIXD Sensor and mobile app today!

Justin Hughes

Recovering autocross and track day enthusiast. Once turned a VW Jetta into a pickup truck. Lives in a van down by the river. Dream car: 2001 Subaru WRC rally car.

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We’re here to help you simplify car care and save, so this post may contain affiliate links to help you do just that. If you click on a link and take action, we may earn a commission. However, the analysis and opinions expressed are our own.


About the Author

Justin Hughes

Justin Hughes

Recovering autocross and track day enthusiast. Once turned a VW Jetta into a pickup truck. Lives in a van down by the river. Dream car: 2001 Subaru WRC rally car.

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