How to know when a knock sensor is bad?

Written by louise balle
  • Share
  • Tweet
  • Share
  • Email

The knock sensor is a small part on a car engine. It helps regulate the air-fuel mix that enters the engine and notifies your car's computer when the engine is knocking. It stops the fuel from exploding in the cylinder and allows it to burn smoothly as it should. A bad knock sensor can cause performance issues and strange noises in the car. There are a few ways that you can determine if you need to replace the knock sensor.

Skill level:


  1. 1

    Listen for a knocking or bumping sound under your bonnet, particularly around the engine. This is the most telling sign of a possible knock sensor problem. A persistent knocking sound means that the knock sensor is broken or cracked and not communicating with your car's computer to correct the problem. The knocking sound is most common when you are driving at high speeds.

  2. 2

    Monitor your gas mileage. When the knock sensor is bad your gas will burn quicker, so watch your gas gauge daily. If you are using more gas to drive the same distance, then there could be a malfunction that involves your knock sensor.

  3. 3

    Check your car for sluggishness and acceleration issues. When the knock sensor is bad, the car will not reach higher speeds as quickly---the engine will have to work harder to reach the desired speed.

  4. 4

    Get a diagnostic test done to confirm your suspicions. Go to a mechanic or auto parts store and have this test done on your car. Some major auto parts stores offer this service for free, since it could lead to a sale.

Tips and warnings

  • Get your knock sensor fixed promptly when you confirm that this is the problem. Expect to pay around £97 to £130 for the part plus labour (Reference 3). It is possible to replace your own knock sensor, but this job should only be done by someone who is very familiar with car engines and has the ability to safely get underneath the car to reach the part.

Don't Miss

  • All types
  • Articles
  • Slideshows
  • Videos
  • Most relevant
  • Most popular
  • Most recent

No articles available

No slideshows available

No videos available

By using the site, you consent to the use of cookies. For more information, please see our Cookie policy.