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Can A Bad Serpentine Belt Cause Check Engine Light?

The serpentine belt powers the alternator.

Your serpentine belt is the long rubber belt that links together and powers several of your engine components when the engine is running. Unfortunately, this belt can wear out and cause problems with your engine.

If the serpentine belt goes bad, it can cause a check engine light to come on. This is because your belt powers your alternator, which in turn powers most of the electronic components of your vehicle. If these components lose power, the computer will trigger a fault code that will cause a check engine light.

Below are some signs and symptoms to watch out for if you suspect you may have a bad belt.

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    The serpentine belt powers the alternator.
    The serpentine belt powers the alternator.

    What Are The Signs Of A Bad Serpentine Belt?

    The most obvious sign that you have a bad serpentine belt is a squealing sound from your engine compartment.

    A serpentine belt is almost always made of rubber. Because of the heat and strain put on it by constant use, it will stretch and wear out over time.

    This will cause the belt to start squealing as it gets loose and isn't being turned properly by the engine pulleys that control it.

    A bad serpentine belt will also have a distinct look to it. A normal good belt will have a smooth appearance, with dark and supple rubber. A belt that has worn out will look cracked or frayed and will begin to look shiny from heat damage.

    There are also several problems with your engine performance that a bad belt can cause. A few examples are listed below.

    Over time a serpentine belt will wear out.
    Over time a serpentine belt will wear out.

    What Problems Can A Bad Serpentine Belt Cause?

    The serpentine belt controls several critical engine functions, and you should not drive without one, as your vehicle is bound to fail shortly.

    The most immediate problem will be alternator failure.

    The alternator powers your electronics when your engine is running and keeps your battery charged.

    If your belt stops powering your alternator, most electronics won't work.

    If you notice that your headlights and dashboard lights are dim, your radio stops working, or any other electronics malfunctioning, this could be a sign of a bad belt.

    The serpentine belt sometimes controls the water pump, which sends engine coolant through your engine and radiator to keep the engine cool.

    The serpentine belt also powers the power steering pump, so you may begin to notice that your car is getting harder to steer.

    Steering problems can be caused by a belt that isn't working correctly.

    Serpentine belts are grooved to prevent slipping.
    Serpentine belts are grooved to prevent slipping.

    What Does It Sound Like When Your Serpentine Belt Is Going Bad?

    A serpentine belt going bad will start making a high-pitched squealing sound.

    This may only happen when you start your car since this is when the most strain is put on the belt.

    A belt stretched to the point of failure will begin squealing almost constantly whenever the engine runs.

    This squealing sound is a sign that your belt needs to be replaced.

    Will Battery Light Come On If Serpentine Belt Is Bad?

    If the battery light on your dashboard comes on, it's another sign that you may have a bad belt.

    Your serpentine belt powers your alternator, which charges your battery when the engine runs.

    If the belt stops powering the alternator, your electronics will begin drawing power directly from your battery.

    This will cause it to quickly lose power since the alternator isn't charging it.

    At this point, your battery light will indicate that your battery doesn't have the correct amount of charge to work correctly.

    Can The Belt Tensioner Cause The Check Engine Light To Come On?

    The serpentine belt has a special pulley designed to keep the correct amount of tension on it as it's running.

    This pulley is called the belt tensioner, and it usually uses a spring to push against the belt and keep it tight.

    This tensioner pulley can also wear out over time, which will cause the belt to get loose.

    If this happens, it will have the same effect as a belt stretched out and can't stay tight.

    The lack of tension on the belt will cause the check engine light to come on since the engine components will begin to stop working correctly.

    How Expensive Is It To Replace A Serpentine Belt?

    A serpentine belt is a relatively cheap part to replace.

    The belt itself will typically cost between $20 and $80, depending on the model of your vehicle.

    If you replace it yourself, you can save the additional labor cost of a mechanic. If not, you will pay another $50 to $100 in labor costs to replace the belt.


    If your serpentine belt has gone bad, it can cause a check engine light to come on.

    Thankfully, this can be a cheap and easy fix, so it shouldn't be something to worry too much about.