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Bad Knock Sensor Symptoms In 2022 : [ Updated Guide ]

Bad Knock Sensor Symptoms In 2022 : [ Updated Guide ]

Modern cars have several sensors built into them. These sensors have their respective functions to carry out. As a car owner, you might have heard of the knock sensor. This isn’t one of the extensively discussed components of your car. However, the knock sensor goes a long way in securing the engine of your car.

This explains why you should be knowing the signs of a bad knock sensor. Like most components in cars, you need to replace the knock sensor at the right time.

What is a knock sensor?

The knock sensor, present in the car’s engine, happens to be a sophisticated listening device. It is capable of detecting the noises in the engine arising from detonation, or instances where fuel explodes in the cylinder of the engine.

The device can make necessary adjustments in the ignition timing accordingly. So, in case the component falters, there would be no proper regulation of the detonation. This would lead to severe damage in the engine. Ultimately, you would be draining your resources on expensive repairs.

Now you know why it’s important to detect the signs of a faulty knock sensor. Once you know that the component is not functioning properly, you can get it replaced immediately. This way, you won’t be shelling out money unnecessarily on repairs.

Bad knock sensor symptoms

In case the knock sensor in your car fails, you would get to know about the issue through some common symptoms. These include:

1. Unnatural behavior of the engine

In the first place, you might notice a difference in the way your car navigates, or the noises that its engine makes. Drivers often look out for particular sounds to detect possible issues with their vehicles.

In case you hear a noise from the engine, it can point to a faulty knock sensor. In this case, the noise would be louder. You should hear a thumping noise if the knock sensor goes bad.

Besides, the thumping noise would gradually grow louder, as it wouldn’t be too prominent at the outset. The improper ignition of air and fuel generates this noise in the cylinder. They fail to reach the stage of combustion in the engine.

2. Low acceleration

If you have a faulty knock sensor in your car, you would experience a loss of acceleration. Particularly, when you try to pick up speed on highways, your car won’t be able to accelerate fast.

Although other technical glitches in your car can lead to poor acceleration, it happens to be a sign of a bad knock sensor as well. The low acceleration occurs since the engine reduces its power output in an effort to mitigate potential damage to your car.

3. Check engine light

Well, you can easily detect an issue with the knock sensor by observing the check engine light. Some of the common error codes associated with the problem include DTC P0332, DTC P0327, and DTC P0325. When you come across these trouble codes, you can identify the problem with your knock sensor. So, you need to visit a trusted mechanic to get the glitch sorted.

4. Poor fuel economy

A problem in your knock sensor would probably give you poor fuel economy. This happens because your vehicle would strive to use up more fuel in an attempt to bridge the combustion gap.

The knock sensor in your car adjusts the timing while controlling the air. It ensures that the most appropriate amount of fuel finds its way to the combustion chamber.

However, when the knock sensor malfunctions, the computer in your car tries to keep the vehicle running. Eventually, it pumps the fuel more, resulting in poor fuel economy.

Since other issues can also lead to poor fuel economy, talk to the mechanic and let them carry out a thorough diagnosis.

5. Low engine power

Apart from affecting the ability of your car to accelerate, a faulty knock sensor would also lead to a loss of torque and speed. This happens as the engine’s default valves refrain from optimizing the performance.

This prevents the engine to generate excessive force. That can potentially lead to additional damage. So, the computer in your car reduces the amount of force or power that the engine is capable of delivering.

6. Emission issues

With a faulty knock sensor, you would notice excessive emissions from your car. The engine would encounter overheating issues when the knock sensor malfunctions. In the end, your car can end up failing the emission tests.

In some cars, the manufacturers integrate the decreased acceleration safety feature. In case the engine doesn’t perform well, the emission rate would reduce.

Until you sort the issue out, the car would be in low gear. Besides, some drivers refer to this situation as the ‘limp mode’.

During this time, the car would run slow, and the engine performance wouldn’t be optimal. When you are in this mode, you won’t be able to travel beyond a particular speed. The car would refuse to travel in the higher gears.

What happens if the knock sensor is bad?

As we discussed, a bad knock sensor would lead to the unchecked detonation of fuel in the combustion chamber of the car’s engine. This can lead to several complications. To sum up, let’s check what can happen if your knock sensor malfunctions.

  • Knocking sound from the engine
  • Poor fuel economy
  • Lack of acceleration in the car
  • Low engine power
  • High emission levels
  • Check engine light coming up
  • Catalyst damage

What does a bad knock sensor sound like?

A malfunctioning knock sensor would produce a knocking or pinging noise. This happens when the ignition of the fuel and air mixture takes place too early owing to detonation or excessive heat.

Besides, some other issues can also lead to early ignition. This leads to excessive pressure in the cylinder, like the damaged pistons rings. So, you get to hear the pinging noises.

These noises occur when you drive the engine at higher RPMs, particularly when you pick up speed. Also, they happen when the engine produces more vibrations, leading to pressure and temperature changes in the cylinders. Eventually, it leads to the knocking noises. If you happen to ignore this trouble for too long, your engine might sustain damage.

Can I drive with a bad knock sensor?

Technically, it is possible to drive with a faulty knock sensor, although experts recommend not to do so. You wouldn’t like the ride quality, besides exposing the vehicle to damage.

The engine would produce thudding and thumping noises, besides sustaining damage over time. Also, you would not like the jerks, constant sounds, and slow acceleration.

Ignoring a bad knock sensor can be expensive, as you would have to refuel your vehicle more frequently. Shelling out a few hundred dollars upfront can save you expensive repairs and fuel costs later on.

Can a bad knock sensor cause rough idle?

Yes, if you have a faulty knock sensor, you would experience slow acceleration and rough idling. Your car would lack engine power and acceleration, besides producing a lot of jerks.

How much does it cost to repair a knock sensor?

On average, replacing your knock sensor would require you to shell out anything between $250 and $350. This amount largely depends on the repair shop you visit and the model of your car.

It would be wise to carry out a thorough diagnosis before you carry out any sort of repair or replacement. Otherwise, you would be squandering your financial resources by changing the wrong components.

The cost of aftermarket knock sensors can range up to $100. However, the OEM components would require you to shell out more.

In case you are comfortable with a DIY repair, you can save the labor charges. This can range between $150 and $250. Based on the model you own, the complexity of accessing the knock sensors might vary.


Your car can land up on several technical glitches arising from bad knock sensors. Most commonly, the vehicle would fail its emission tests, producing high levels of CO and HC. Besides, it would encounter issues like rough idling, slow acceleration, and low power.

In cars with electronic ignition or distributor-less ignition, replacing the knock sensor would be fairly easy. However, if your car has a distributor system, it would be difficult to replace the component.

In any case, it would be wise to seek professional assistance from an authorized mechanic while addressing the issue. This ensures that you would be replacing the right parts, thereby seeking cost-effective services.