Can Aftermarket Exhaust Cause Check Engine Light [Explained]

Aftermarket exhaust systems are getting increasingly popular as it’s known to increase power and give better sound. But they’re also notorious for triggering the CEL. So, can aftermarket exhaust cause the check engine light to turn on?

can aftermarket exhaust cause check engine light

The short answer is yes, it can. An aftermarket exhaust system will not necessarily trigger the CEL, but it’s possible. Especially if the installation hasn’t been done correctly and there are leaks.

You need to consider many factors to determine if the exhaust is causing the CEL to come on. We’ll discuss all of it in this guide. So, let’s dive into it!

Can Aftermarket Exhaust Cause Check Engine Light [3 Easy Fixes]

An aftermarket exhaust can cause the check engine light to turn on in a few situations. Here are the most common instances that’ll make it happen:

Note: You can also read how to fix white smoke from the exhaust that smells like gas.

1. Incorrect Installation

When installing the new exhaust system isn’t done correctly, it can cause leaks. And leaks will inevitably lead to the check engine light being turned on. There are many ways you can go about diagnosing this issue.

incorrect  installation of the new exhaust system

The first is the old-school method of feeling the leaks by placing your hands close to the exhaust pipes. If you do so, you’ll have a good idea of where the leak is coming from.

The other method is to use an OBD-II scanner and see what error codes pop up on it. If it shows issues with the Oxygen sensors and shows emissions, it’s most likely an installation problem.


The pipes need to be sealed correctly such that there are no exhaust leaks. Not knowing which clamps to cut off and the proper direction of installation has probably caused this issue in the first place.

So, fixing these issues will take care of the problem. So, the aftermarket exhaust needs to be reinstalled correctly. If you don’t feel comfortable doing it yourself, it’s a good idea to hand it over to an expert.

He may have to weld certain parts to seal the leak. There’s also a chance that you may have dropped an oxygen sensor or dinged it. So, be on the lookout for that and correct it if needed.

2. Aftermarket Catalytic Converters

Some aftermarket exhaust systems include replacing the stock catalytic converters in your vehicle. If that’s the case with you, it could be the reason behind turning on the check engine light after the cat back exhaust install.

aftermarket catalytic converters

The P0420 or P0430 error codes are the strongest indicators of issues with the catalytic converter. Your driving style and the number of catalytic converters in your car play a role in whether it functions properly.

 P0430 error codes

The other symptoms of a failing or mismatching catalytic converter are:

  • The engine is running rough.
  • Poor acceleration from the engine.
  • The exhaust smells like rotten eggs.


Do you see the check engine light on after the new exhaust installation, along with the error codes? If yes, it’s evident that the new catalytic converter doesn’t match your engine’s requirements.

In that case, you’ll have to get it replaced. It’s a good idea to replace the O2 sensors and spark plugs when you change the catalytic converter. Because issues with the engine misfiring can cause the new CC to go bad soon.

3. ECU Incompatibility

Still confused will an aftermarket exhaust cause a check engine light? When the engine shows the CEL, it’s primarily due to the ECU (your car’s computer) getting warning signals from the O2 sensors.

 incompatibility car ECU

When you don’t use the right parts in the new exhaust system, they may not be enough to satisfy the reading of the sensors.

Besides, there are engines in which the exhausts are designed to help close the exhaust valves.

Fitting an aftermarket exhaust in place of the stock can increase emissions as the valves no longer close properly. The fuel injectors can also cause the check engine light to come on.


The mismatch between the sensors in your car and the new exhaust parts is causing the issue. In that case, the simplest solution is to go back to using the stock system.

But if you’ve made up your mind about using aftermarket exhausts, research what parts will match your vehicle. Then, go on to replace the exhaust. Otherwise, you’ll end up in the same mess again.

Can Aftermarket Exhaust Damage Car Engine

Before discussing the impact of an aftermarket exhaust system on the engine, remember that there are different types. Here are the most common exhaust types you’ll frequently encounter:

Axle Back System: It refers to replacing the exhaust from the rear axle to the muffler.

Cat Back System: This means replacing the exhaust starting from the catalytic converter to the muffler.

Header Back System: This means replacing the entire exhaust system in your vehicle.

You can increase your car’s power by replacing the exhaust for a few models.  It can also lead to better fuel economy and better sound. So, can it damage the engine at all?

As long as it’s installed correctly and you select compatible parts, there’s no reason it’ll damage the engine.

It’s a common myth that low-restriction aftermarket exhaust can damage exhaust valves. But that’s not the case.

However, such exhaust systems will not damage the engine only if the replacement is done correctly.

Otherwise, it can cause the check engine light to turn on. In the long run, it can damage the engine by reducing fuel efficiency and increasing emissions.

Will Muffler Delete Cause Check Engine Light

Muffler delete is the process of removing the muffler from an exhaust system. It’s replaced with a muffler delete pipe, and the exhaust tip is welded. As the exhaust flow from the vehicle increases significantly due to this process, it can trigger the check engine light.

car muffler delete pipe

A muffler delete is most likely to show error codes in modern vehicles. But if you have an older vehicle, there’s no chance it’ll throw any codes. So, why does muffler delete cause check engine light without showing codes?

That’s because the muffler doesn’t have any sensor of its own. The O2 sensor signals the ECU that the car has an improper air-fuel ratio. That’s what triggers the CEL to come on.

Does Resonator Delete Cause Check Engine Light

The resonator delete will not cause the engine light to come on as it only impacts the exhaust system’s sound. As long as you don’t do any other exhaust changes along with it, the CEL won’t come on.

Resonator delete is a great way to optimize the pulses in your vehicle and improve power production. You can improve the sound your car makes without making the airflow worse.

However, if the resonator isn’t removed correctly, it can affect the other parts of the exhaust system, including the muffler and catalytic converter. Any issues with them can easily trigger the check engine light.

What Does Exhaust Smoke Mean

Seeing smoke coming out of your car is never a good sign. Depending on the color of the smoke, it can mean a few things. Here’s what each of the colors could mean:

Blue Smoke

It indicates oil burning in the combustion chamber. Issues with the valve seals, valve guides, worn cylinder walls, PCV systems, and piston rings are the most common culprits behind it.

Black Smoke

It means that the engine is running rich and burning more fuel than necessary. A clogged air filter or dirty fuel injectors can lead to this issue. So, check these components and replace them if needed.

black smoke

White-Grey Smoke

Seeing whitish-grey smoke indicates coolant burning in the combustion chamber. It’s not a good sign at all. It indicates issues with the cylinder head, head gasket, or engine block.

How To Make The Check Engine Light Go Away

First of all, remember that the check engine light indicates that there’s a severe issue with your car. It must be corrected as soon as possible to maintain the vehicle’s long-term health.

So, you shouldn’t cheat the system and try to reset it without correcting the underlying issue. You already know the most common causes of it by now. With an OBD-II scanner, you can diagnose the exact point in most cases.

Fix the issue and then reset the check engine light. If you’ve solved the problem correctly, the check engine light won’t return anymore. But if the problem persists, you must keep diagnosing and solving the issue that’s triggering it to turn on.

How To Prevent Exhaust System Issues

Prevention is always better than cure. And you can stay on top of things by having your car inspected every couple of years.

It doesn’t matter if you’ve seen any obvious problems with the exhaust system at this stage.

You’ll find trouble areas early on and can correct them when needed. It’ll keep any major component from going out and keep your exhaust system healthy over a long period.


Should you drive when the check engine light is on?

You shouldn’t drive the car if the CEL stays on. Normally, a blinking CEL means you can address the problem in a while. So, you can drive the car with a blinking CEL but make sure you monitor it.

What is the main job of the exhaust system?

The main thing that an exhaust system does is reduce carbon emissions. It does so by taking the exhaust gases away from the people in a vehicle and cleaning them before releasing them into the environment.

Do the muffler and exhaust do the same job?

A muffler and an exhaust are components of the exhaust system, but they don’t do the same job. The exhaust reduces carbon emissions from the engine. And a muffler reduces the noise while the exhaust does so.

What are the parts that make up an exhaust system?

Components like the exhaust manifold, catalytic converter, muffler or silencer, resonator, tailpipe, O2 sensors, and connecting pipes together form the exhaust system in a car.

Does a muffler have any sensors?

No, there are no sensors in a muffler. However, there are sensors located before the mufflers in modern cars.

Will removing the resonator increase carbon emissions?

No, it won’t. The job of the resonator is only to improve the vehicle’s sound. Removing it only changes the sound. It has no impact on the emissions your car produces.


Can aftermarket exhaust cause a check engine light? Hopefully, now you know how and why the CEL comes on after completing this guide. Diagnose what’s causing the trouble and fix it to get rid of the check engine light.

If you can find the right parts, don’t install an aftermarket exhaust system in your car. Get your car checked out at regular intervals to catch problems early on and prevent any major damages.

Comment below if you have any questions regarding aftermarket exhaust systems.

About John M

John contributed as a technical head at an automobile company just 2 years after his post-graduation in Automobile Engineering. He loves to lead a free life, so he left his job & started blogging. Now, he does research on every automotive problem, part & product and seeks a better solution & best products & shares his findings with his readers to help them as well as to minimize their struggle.

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