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A knock sensor is one of those tiny components in your vehicle that you never notice until there is an issue. This sensor is located on the cylinder head, intake manifold, or engine block. And when an issue does arise, it requires an immediate response. A solid understanding of the functionality of your knock sensor is essential so you know when it goes wrong and what you should do.

Here we will break down the basics of what your knock sensor does and why it is important to your car. We’ll also look into driving without one, or with a faulty one, and the possible consequences. Finally, we will dive into replacing it and how much it may cost.

The Function of a Knock Sensor

The knock sensor serves a handful of critical purposes for your car. The first is that the component detects and prevents engine damage—specifically, preignition and detonation due to damage of the pistons, rods, valves, gaskets, and plugs. The sensor is able to detect knocking and pinging noises that are imperceptible to the driver’s ear. When the sensor detects this, it can retard the spark plug timing to prevent any damage.

A second thing it does is provide for the overall protection of the car’s engine. It monitors engine performance and will send a signal to the car’s computer, the Powertrain Control Module. The knock sensor is on constant sentinel mode, always ensuring that your engine is safe and running properly.

A third thing it does is make certain your car is fuel-efficient. This is done by optimizing the amount of power to the engine via balancing the fuel-to-air mix. This makes sure that your car runs properly and isn’t struggling to get down the road, ultimately saving you money.

Can You Drive Without a Knock Sensor?

Technically, you can drive without a knock sensor. But should you? Definitely not. A damaged knock sensor will not stop your car from running immediately, but it will in short order.

The first symptoms of a damaged knock sensor are decreased acceleration and a hot engine. You may also hear knocks from your engine. Your vehicle  will start to eat up gas more quickly than expected. You may even notice a burning smell. Overall, you will notice that your car is not performing the way it should. Your check engine light should come on. That is not a signal some respond to quickly, but unless you want to end up replacing your entire car engine, you will want to address it.

Yes, you can temporarily drive with a faulty knock sensor. But as soon as you see signals that there is something wrong, you want to replace it before there is much more extensive—and expensive—damage.

Replacing car knock sensor

How to Replace a Knock Sensor

This component is hardy enough to last about 150,000 miles before it begins to wear down. That being said, there could be other issues within your car to cause it to break down sooner. So now that you’ve determined your knock sensor needs to be replaced, how do you go about doing so?

The cost of replacing the sensor is not astronomical. The part itself typically costs between $65 and $200. Add labor costs onto that, unless you are exceptionally mechanically adept. Your best bet is to take it to an auto shop or hire an independent mechanic to fix it.

If you hire a professional, they will be able to determine what knock sensor is used and get a suitable replacement. But if you choose to do it yourself, you’ll need to determine what type of sensor you have.

There are two different types of knock sensors: vibration detection and pressure measurement. Vibration detection sensors are most common, and within those are three different types of sensors. These are inductive resonant sensors, piezoelectric resonant sensors, and piezoelectric non-resonant sensors. What it boils down to is how they sense engine knocks, whether through a vibration plate, frequency detection, or a spring.

The second type is one that detects engine knocks via measuring the internal pressure of the cylinder. These types are typically alongside the spark plug. An engine knock will cause a high-frequency noise that superimposed on the combustion pressure waveform. Your knock sensor will filter this waveform to detect the engine knock.

Top Brands of Knock Sensors

If you do choose to purchase a replacement knock sensor yourself, or have a mechanic inquiring about the brand, you will want to be aware of what choices there are. Investing in one that is not reliable will just cost you more money in the long run. Here, we give a brief overview of the top brands for good knock sensors along with approximate price, as well as brands to avoid.

  • General Motors supplies knock sensors for Chevy Silverados, Tahoes, Express, and Suburbans for around $35. General Motors is known for a variety of reliable products for cars, and with their availability across retail and online, it is quick and easy to find what you’re looking for.
  • ACDelco offers a GM Original Equipment Ignition Knock Sensor for just under $45. This is a good choice for most vehicles and will be reliable and long-lasting. It’s a subsidiary of General Motors, so it also comes with the benefits of a large selection.
  • Beck Arnley has a knock sensor for about $40 that has proved to be high-quality and durable. Their focus is on providing OE (Original Equipment) parts, so that will give you some peace of mind in ensuring you get the exact same part you are replacing for your car.
  • Honda offers a replacement knock sensor direct from the factory. One with a manufacturing number of 30530-PPL-A01 costs $85. However, there is the assurance with this higher price that you are getting a brand new part, direct from the manufacturer, suited exactly for your vehicle.
  • Huijin has a knock sensor for only $12 and it comes with a harness wire. Despite it being specifically made for a variety of Nissan models, you get what you pay for and it doesn’t always fit correctly. It is specifically made for the Infiniti G20, I30, J30, Q45, Qx4, Nissan 200sx, 240sx, 300zx, Altima, Frontier, Lucino, Maxima, Nx, Pathfinder, Pickup, Quest, Sentra, Tsuru, and Xterra.
  • Autex supplies new and high-quality aftermarket knock sensors for under $10. They provide a compatibility chart to see if it will match with your vehicle’s needs. However, there are reported issues of online orders not arriving with all the parts bought, and issues with car compatibility.
  • Toyota offers a knock sensor for a staggering $141, well beyond comparative products on the market. With this, you do get peace of mind that it is directly from the manufacturer and is brand new. The manufacturing part number is 89615-12090. It’s proven to be of excellent quality and long-lasting. But the price jump from similar products doesn’t seem to offer any viable differences.
  • Hyundai has a knock sensor for around $20, direct from the manufacturer, with a manufacturing part number of 39250-2G100. Again, by going with the OE, you are ensured the exact fit, the exact part, and have the guesswork taken out for you. This price is also quite reasonable compared to others.

On the topic of getting Original Equipment products, it is always a good idea to go with a knock sensor that is brand new or direct from the manufacturer, rather than aftermarket. There have been a multitude of reported issues with aftermarket knock sensors that range from an improper fit, extreme difficulty to install, to a lifespan of only a few days for the product. It can be hard to pass up a good bargain, however, for such a critical piece of equipment for your vehicle, as prices can be too good to be true. It is worth spending the extra money to ensure your car’s continued safety and proper functioning.

Summary

A knock sensor is an essential part of your vehicle that you want to ensure is always in good shape. A faulty or worn out one could result in losing your car. Always pay attention to any decline in performance or strange noises, particularly if your car is older.

The function of a knock sensor is to regulate, monitor, and protect your car’s engine from damage. Symptoms of a damaged knock sensor include decreased speed, issues with car handling, a burning smell, a knocking noise, and a check engine light. These replacements are best done by a professional and can cost upwards of $200.

FAQs

Q: What happens if I ignore my damaged knock sensor?

A: Your car could have an engine failure if you ignore a damaged knock sensor. You’ll then need to replace your whole engine.

Q: Could I install the knock sensor myself?

A: Maybe. If you are good with mechanics, then it may be easy for you. If you are unsure, it’s best to hire a professional.

Q: Where is the knock sensor located?

A: The knock sensor is located in the cylinder head, intake manifold, or engine block.

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