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Can An Exhaust Leak Cause A Check Engine Light?

A mechanic inspecting an exhaust system.

Your car's exhaust system can occasionally develop a leak, which can be a cause for concern.

An exhaust leak can cause your check engine light to come on because it can affect your oxygen sensors' fuel/air mixture reading. This will cause a bad sensor reading, sending a trouble code to your engine computer.

Keep reading to find out more about the problems you may encounter if you have an exhaust leak.

Table Of Contents [show]

    A mechanic inspecting an exhaust system.
    A mechanic inspecting an exhaust system.

    Will Exhaust Leak Give A Check Engine Light?

    An exhaust leak can cause a check engine light in your car.

    One or more oxygen sensors monitor your exhaust system, which reports the air and fuel levels sent through the exhaust manifold and the tailpipe.

    If these levels are thrown off from their normal measurements, the oxygen sensors will detect this and send the information to your engine computer.

    When this happens, the computer will turn on the check engine light to warn you that there is a problem with your vehicle that needs your attention.

    Will An Exhaust Leak Throw A Code?

    An exhaust leak that lets extra air, known as "unmetered air," into your exhaust system will cause the oxygen sensors to register this as a trouble code.

    The oxygen sensor will send this code to your engine computer, which will store the code. You can then read the code with a code reader, which you can use to pinpoint where the problem has occurred.

    What Does An Exhaust Leak Sound Like?

    An exhaust leak that happens before the muffler will cause an unmistakable loud rumbling noise under your car.

    If the leak occurs after the muffler, it will still be loud enough to notice, but the muffler will help to reduce a little of the noise.

    An oxygen sensor can trigger a check engine light if there is an exhaust leak.
    An oxygen sensor can trigger a check engine light if there is an exhaust leak.

    What Are The Symptoms Of An Exhaust Leak?

    Thankfully, you can easily identify an exhaust leak because it has a few signs that are hard to miss.

    1. Loud noise under your car

    Your exhaust system is designed to reduce the noise level caused by your engine's combustion process.

    If your car develops an exhaust leak, it can reduce the ability of the muffler to keep your engine running quietly.

    If you start noticing loud noise under your car when your engine is running, it's a sure sign you have an exhaust leak.

    2. Exhaust smell around or inside your car

    Ideally, the tailpipe carries your car's exhaust to the back of your vehicle and away into the air.

    A leak in your exhaust, especially toward the front of the exhaust pipes, can cause the exhaust fumes to collect around your car instead.

    This can be dangerous because it can cause toxic exhaust fumes to be pulled inside your vehicle while running.

    3. Problems with stalling or misfiring

    As stated before, your engine measures your exhaust fumes to adjust the fuel/air mixture to the correct levels to run its best.

    An exhaust leak can throw off these readings, causing your engine to either use too much or too little fuel.

    If it adjusts too much in either direction, it can cause your engine to stall out, run rough, or misfire in one or more of the cylinders.

    4. Exhaust backfiring

    This goes along with other loud exhaust noises, but it's worth it's own listing. If you've heard a car backfire, you know it's impossible to miss.

    A backfire happens when unburned fuel inside your exhaust pipes gets hot enough to ignite, causing it to combust inside the pipes.

    This will cause a loud, sharp bang that sounds similar to a gunshot, which will get the attention of everyone around you at the time.

    What Problems Can An Exhaust Leak Cause?

    An exhaust leak can lead to several potential issues you should watch out for, so you should get it fixed as soon as possible.

    The leaking exhaust fumes can collect inside your vehicle, harming you and other passengers.

    It can also cause poor performance in your engine, such as stalling, sputtering, and misfiring.

    A mechanic inspecting a recently installed muffler for any leaks.
    A mechanic inspecting a recently installed muffler for any leaks.

    How Expensive Is It To Fix An Exhaust Leak?

    The cost to repair an exhaust leak depends on the location and severity of the leak.

    For example, if the leak is bad enough to require a new section of pipe to be welded in place, it will be more expensive than a crack that needs to be patched up.

    The cost also depends on who does the repair work for your car. For example, if you or a friend have welding knowledge and equipment, you could repair it for much less than a muffler shop would.

    The total repair cost for a leak could be anywhere from less than $100 to several hundred dollars. It all comes down to what is required to fix the problem.


    A leaky exhaust system can cause a check engine light, which will give you a hint that it's time to have it checked out.

    It's worth taking this problem seriously, but it can also be an easy fix if caught early and not given a chance to get worse over time.