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What Is The Cost To Replace A Knock Sensor: What You Need To Know!

Cost To Replace A Knock Sensor

A key part of the inner workings of your car, the knock sensor is a crucial mechanism that detects pre-ignition and pre-detonation, keeping your engine safe and healthy. 

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When your engine vibrates, a sensor tells the internal computer how big the vibration was. If the vibration is large enough that it is called a “knock,” then the knock sensor will tell the engine that there is a problem. If this sensor fails, you will need to get the sensor replaced. In this case, the average cost to replace a knock sensor is $100. 

What is a knock sensor?


When you press on the gas pedal in your vehicle, and you hear a soft noise coming from the pedal or the engine under your hood, this is what is called “engine knock.” Hearing this knocking or clunking sound, along with additional engine noise and the exhaust is the main sign of engine knock and can turn on the knock sensor. What you are hearing when this happens is pre-ignition, which typically occurs when there is a pocket of the air and fuel mixture lighting and igniting before the flame comes out from the spark plug. 


If this happens in your car, a small electrical current goes off near the explosion, increasing the cylinder’s pressure. In most cases, the engine knocking can lead to severe damage in the engine, causing an expensive repair or complete replacement, meaning that the bad knock sensor can damage the engine and leading to a high knock sensor cost. If you are wondering how much it cost to replace a knock sensor, the answer is a lot.


In an older engine where the ignition timing cao fit your needs, the engine knocking can be analyzed and fixed by slowing down the timing just a little. Also, water injection could be a potential solution. By figuring out the solution of the engine knocking issues, you can successfully lower the total cost to replace a knock sensor.  

The Function of the Knock Sensor


Now that we have answered your question of what a knock sensor is, we must know the main function of this part. To see how important this part is in your car, you must know the function of this mechanism in your vehicle. A car’s control module uses a specific computer that optimizes and perfects the timing of the ignition of the engine. This computer’s decision impacts various parts in the car, like the mileage, power, and engine’s lifespan. If the computer is not working correctly, this can lead to a higher cost to replace a knock sensor. 


  • Altering Ignition Timing



At high engine speeds, the control module is in charge of turning on the ignition timing, allowing the air to fuel mixture in the engine time to burn and combust at the right moment. However, if the ignition time is too delayed during the combustion process, it could lead to pre-ignition and pre-combustion. This uncontrolled engine ignition is also known as engine knock. The pre-ignition or pre-combustion leads to a high cost to replace a knock sensor. 


  • Delaying the Timing of the Spark



To prevent these early vibrations and explosions from happening in your vehicle, the knock sensor is in charge of analyzing and noticing the vibrations from the pre-ignition, sending a signal to the electronic control module, and delaying the timing of the spark to avoid the detonation. For the knock sensor to work correctly, you might need to look into a replacement and the cost to replace a knock sensor. 

What Is The Engine “Knock”?


Under traditional, every day driving situations and standard performance qualities of the car’s engine, the engine control unit is responsible for triggering the spark. The main function of this spark is to ignite the air to fuel mixture within the chamber of the engine to properly start the engine and the car. Since the air to fuel mixture takes a certain amount of time to burn, the engine control unit adjusts the timing of the ignition to provide a balance of both the power and efficiency, leading to a lower cost to replace a knock sensor. 


Any delay in the spark of the ignition timing can result in a decreased power and cue the engine knock to occur. If the spark process begins too soon, this result would cause self-ignition within the chamber and can damage the engine, leading to an eventual engine replacement that can be very expensive. 

What Causes a Knock Sensor to go Bad?

There are various reasons why your car engine knock sensor might go bad over an extended period of time. There are many solutions and root causes as to why you might have a failing or damaged knock sensor. Knowing the cause can help you figure out the main solution and give you an idea of the cost to replace a knock sensor. 


  • Check Engine Light



The first reason for a damaged knock sensor could be the illumination of the check Engine Light. If the computer does not recognize the sound in your vehicle, then it can automatically turn on the check engine light. Although this can come on for numerous other reasons, like a loose fuel cap, catalytic converter failure, spark plug issues, ignition coil damage, or bad spark plug wires, the engine light wont turn on from the abnormal sounds. In this case, you should bring your cat to a mechanic to evaluate the cost of replacing a knock sensor. 


  • Misuse of the Vehicle



The second cause of a bad knock sensor could be the misuse of the car – if you are handling your vehicle roughly, and causing poor acceleration and poor fuel economy, the car's performance will suffer and it can damage the knock sensor. It can even go bad if you are removing the knock sensor in the wrong way. If you push the connectors the wrong way this can cause the sensor to go out of alignment and break fragile parts. 

Symptoms of a bad knock sensor

When engine knock occurs in your vehicle, the knock sensor is responsible for keeping your engine in a high-performing shape and preventing a bad knock sensor from damaging the engine to the point of replacement. Engine detonation occurs during the internal combustion process. During the combustion, if the fuel in your car’s cylinder explodes too early and changes the ignition timing, this can lead to faulty timing and a premature explosion. This detonation that occurs too early is often referred to as engine knocking, and can cause a higher cost to replace your knock sensor. 


When a vehicle’s engine starts and turns over while you are driving, detonation is consistently occurring. There is a knock sensor responsible for regulating the engine, detecting the vibrations and the detonations, and sending the voltage to the powertrain control module. If you realize that you need to replace the knock sensor and have looked into the cost to replace a knock sensor, this could be the result of your engine having voltage issues. 


The powertrain control module is in charge of controlling a vehicle’s engine, transmission, and other specific driveline components. These important mechanisms depend on the make, model, and year of vehicle you have, and are crucial to the running of your car. Generally called the PCM, this automotive control unit combines the engine control and the transmission control unit. 


According to Oards, there are main symptoms of a bad knock sensor in your vehicle. 

  1. Engine Warning Light


One of the first symptoms that is the most noticeable for the driver to see when determining the longevity of your engine and knock sensor is the engine warning light. You might notice this show up on your engine dashboard, indicating you may need to look into the cost to replace a knock sensor. Although this can happen due to many reasons, one of the main reasons of hte engine warning light coming on is a poor knock sensor. 


Other reasons that an engine warning light may come on are varied depending on the root cause. One of the main reasons is the oxygen sensor failure, which measures the amount of unburnt oxygen in a car’s exhaust system, sending data to the vehicle's computer and regulating the mixture of fuel and air that enters the cylinders.


Another cause of an engine warning light coming on besides a bad knock sensor that can ruin your engine is a loose fuel cap, which is a crucial part of the fuel delivery system that prevents fumes from leaving the fuel tank. 


  • Loud Sounds



When the knock sensor starts to act erratically and becomes damaged over time, you may hear loud sounds that come from underneath the hood in your engine that can sound just like loud thumping sounds. The longer you go without fixing the catalyst of this issue, the louder these sounds will get. These sounds will only get worse over time and can increase the total cost to replace a knock sensor. 


The reason these noises occur is mainly due to the timing of the ignition of the air and fuel mixture located within the cylinder. Usually in a normal car with a properly working knock sensor, this mixture would reach the combustion point too early. Sounds like this should spur you to immediately take your vehicle to the mechanic so that no further problems arise.


  • Reduced Engine Performance



The worst and most serious symptom that you might notice from the bad knock sensor will usually occur when the internal engine components become damaged or break down after constant use. If you have let the minor problems get worse over time without fixing the bad knock sensor or any of the engine parts, your vehicle will start to suffer. The engine will cause an increase in drag and a jerking while accelerating, resulting in a higher cost to replace a knock sensor. 


You might even notice a burning odor or smell coming from the engine. Usually, this smell is so strong and pungent that it will get into the cabin of your vehicle and can be easily noticed by both the driver and the passengers. If you continue driving your vehicle, this could result in the bad knock sensor and the poor engine components causing the entire engine to be destroyed and requiring a replacement of hte engine or an analysis of the cost to replace a knock sensor. 


  • Engine Replacement



An engine replacement cost is one of the most expensive repairs or fixeds you can have in your vehicle, no matter what kind of make, model and year of vehicle you have. Replacing an engine actually often costs more than a vehicle's overall worth is for the owner. On average, the replacement cost is between $4,000 and $5,000 to replace a 4 cylinder engine. The price is even likely to increase on a V6 or V8 engine, meaning that a high-end, luxury, or sports oriented car can be upwards of $6,000 for an engine replacement. 

Knock Sensor Replacement Cost


In most cases with your vehicle and when your car is running at an optimal level, if you leave the engine knock alone and do not take care of the root issue, it can lead to permanent damage. This quickly will lead to engine breakdown and the need for an engine replacement. This can cause the car to be unable to accelerate smoothly, the car to start to jerk while driving, the car to stall, and the car to drag. 


These signs can also be accompanied by a burning smell that can be very noticeable by both the driver and the passengers. These are sure signs that the engine knock sensor can detect permanent engine damage. 

Average Price


To replace the engine knock sensor, you will pay on average around $200 to $400 to replace the knock sensor. 


The bad knock sensor can damage an engine if you do not replace the part and if the faulty knock sensor has damaged other components. However, unlike an engine replacement, the good news is that you will not have to pay nearly as much to replace a bad knock sensor. If you have a standard vehicle, the average knock sensor replacement cost will usually range anywhere between $120 and $500 on average for the cost to replace a knock sensor. The cost of the parts is generally between $65 and $200, while the labor cost will range between $50 and $350. 


In most situations, the parts cost and the labor costs will actually be pretty equal, with both of these averaging around the $100 mark. If you can find a good deal on spare parts that are used or from independent shops, then this could lower the overall replacement cost, since you will be saving money on the parts cost. 



Knowing the average cost to replace a knock sensor can ensure you keep your car runing healthily for a long period of time. Byu keeping an eye out for hte warning signs, like the engine warning light turning on, loud sounds, and a reduced enegine perforamnce, you can reduce the toal kncok sensor replacement cost. 

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