Bad Knock Sensor Symptoms and Replacement Cost

No one likes to have a car break down in the middle of the road. Many times, this happens due to the failure of the engine. And honestly, you are the one to blame for it. Because you might have ignored all the bad knock sensor symptoms or have no idea what they are. That’s why to save you from all that hassle. We are here to help.

Whenever the ignition time of your car engine crosses a certain point, it causes pre-ignition. This happens with the loss of control. This uncontrolled pre-ignition is called knock. They are pretty much like small explosions in your car engine.

Here comes the functionality of the knock sensor. A knock sensor can identify a pre-ignition and take necessary steps to avoid further harm to your engine. Primarily, it sends some sort of signal delaying spark timing which in turn helps in saving your engine.

So, it’s very important to know when your knock sensor is malfunctioning or is going bad. Now that you know what a knock sensor does. Let’s check out the symptoms of a bad knock sensor.

Symptoms of a bad knock sensor

Some evident symptoms indicate a problem with your knock sensor. The following are some crucial signs of a bad knock sensor.

Engine warning light

Whenever your car engine goes through a problem, you will see it right away on your dashboard. This is the very first symptom of a bad knock sensor. You see an early warning sign lighting up on your dashboard. Never ignore this sign at any cost. Otherwise, it can worsen the condition of your car over time. Also, around this time, you can go for repair without any heavy damage to the engine.

A bad knock sensor isn’t the only reason for an engine warning light. However, it is one of them. Hence, you should consider the warning light as a symptom of a bad knock sensor.

Engine knocking 

A knock sensor, in reality, isn’t an essential part of your engine. The engine can still work well enough without the sensor. However, in some cases, it can lead to engine pinging. This is a vital problem for any car engine. It doesn’t take much time to ruin the whole engine completely. So, if you are facing the engine knocking, that might be an indication of a bad knock sensor.

Disturbingly loud sounds

Another clear sign of a bad knock sensor is a disturbing thump-like sound coming from your engine. And as time goes by, the sound will get louder and louder. As you already know, a knock sensor helps maintain the balance of ignition air and fuel mixture. So, when the sensor doesn’t work properly, the balance stumbles and causes these thumping sounds. It’s best to take your car to the repair shop right when you start hearing the sounds.

Low fuel efficiency 

This is something you will surely notice. When the knock sensor of your car goes bad, you will notice an increase in the fuel consumption of your car. Even though it’s not the only cause of worsening fuel mileage, still it’s one of them. And it’s one of the easier ones to solve. So, if you see your car suddenly has low fuel mileage, you can consider a bad knock sensor here. 

Poor engine performance

This is a very obvious symptom. A knock sensor is a part of your car engine. So, when that doesn’t work properly, it will surely affect the performance of your engine. As clear signs, you can see your car engine jerking and dragging around. That mostly happens when you don’t replace or repair your bad knock sensor. So, this is a sign you will notice after some time.

Bad acceleration 

No one likes when their car has to go through bad acceleration. The whole point of acceleration is to go fast. If your car isn’t going as fast as it used to after acceleration, the knock sensor is probably at fault here. Also, it can affect other parts of the engine that causes a decrease in the acceleration. So, it’s a clear sign of a bad knock sensor. 



Well, these are some ways on how to tell if the knock sensor is bad or not. They can cause other problems too. However, a bad knock sensor can also be a reason for all these problems. 

Can I drive with a bad knock sensor?

If you are wondering, "Can I drive with a bad knock sensor?" then the answer is yes, you can. However, it's not good for a longer period. The longer a bad knock sensor gets without repair, the further damage it does to your engine. Sometimes it can lead to heavy damage to your engine that can completely ruin your car, or it can cost you a lot of money to fix it.

Also, it's not safe for you to drive a car with faulty parts since anything can happen on the road. That's why to replace your bad knock sensor as soon as you notice any of the symptoms.

The Knock sensor replacement cost

Usually, the cost of replacement of a knock sensor depends on the vehicle you use and the service you take. It can range somewhere between $150 to $500 depending on those factors. If you want to know how much does a knock sensor cost, then it can go from $50 to $200 or even more. That mostly depends on the model of your car.

Now, a question that pops up very often, “Can you replace a knock sensor yourself?”. The answer is you can, but you will need some mechanical experience. If you are a beginner, we suggest you keep away from repairing it on your own because you might accidentally damage your car even further.

Opting for a service may cost a lot more than doing it on your own, but it’s worth it as some cars may need specialized treatment where it’s hard to access the knock sensor. In such cases, professional mechanics have to put in a lot of work and charge more. The cost of their labor can go from $60 to $250 depending on how much they had to work for it.

Last Words

So, there you go. We got you everything you needed to know, starting from bad knock sensor symptoms to the cost of replacing them. And knowing these are very important to save yourself from a car breakdown in the middle of the road. Or you have to go through a huge expense due to a damaged engine. I hope this helps you in keeping your car safe from any knock sensor malfunction.


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