How to Diagnose and Fix Engine Knock on Your 2000 Subaru Outback: A Comprehensive Guide

If you own a 2000 Subaru Outback, it’s easy to diagnose and fix engine knock by following this comprehensive guide. Engine knock occurs when fuel ignites prematurely in one or more of the engine’s cylinders, creating a knocking or rattling sound. It can lead to serious damage if not dealt with promptly, so understanding how to diagnose and fix this problem is crucial.

Understanding What is a Knock Sensor and Its Significance

Before you can diagnose an engine knock, it’s important to understand what a knock sensor is and its function. The knock sensor is a component that detects engine knock and sends signals to the car’s computer to adjust ignition timing. This adjustment prevents engine knock, which can cause engine damage in the long run.

Signs of a Damaged Knock Sensor

A damaged knock sensor can create various symptoms in your Subaru Outback. Some of the common indications of a faulty knock sensor that you should look out for include:

  • Decreased fuel economy
  • Engine warning light is on
  • Abnormal engine sounds, knocks, rattles, or pings
  • Reduced engine performance and power
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If you notice these symptoms, it’s best to check the knock sensor for proper functionality.

How to Access the Knock Sensor on a 2000 Subaru Outback

Accessing the knock sensor is relatively simple. It’s located under the intake manifold between the engine block and the firewall. Here’s how you can access it:

  1. Disconnect the car battery to avoid electrical shock
  2. Remove the air cleaner assembly, air intake tube, and coupler
  3. Remove the throttle body and disconnect any hoses attached
  4. Remove the electrical connectors from the injectors, TPS, and vacuum sensor
  5. Remove the four bolts holding the intake manifold and then carefully remove the manifold
  6. Clean the knock sensor and its wiring connector with electronic cleaner to remove any debris or corrosion.

How to Test the Knock Sensor using a Multimeter or Scan Tool

There are two ways to test the knock sensor on your 2000 Subaru Outback: using a multimeter or a scan tool.

Testing with a Multimeter

  1. Disconnect the knock sensor electrical connector.
  2. Set the multimeter to resistance mode and place the probes on the terminals on the connector.
  3. Test the resistance by making noise near the sensing part while watching the multimeter.
  4. A good knock sensor will have a resistance value of around 500Kohms to 620Kohms.
  5. Replace the knock sensor if the resistance value is out of range.

Testing with a Scan Tool

  1. Connect the scan tool to the OBD-II port on your Subaru Outback.
  2. Run a diagnostic trouble code (DTC) scan with the scan tool to check for any faults in the knock sensor.
  3. If the scan tool displays a knock sensor code, perform a signal check using the scan tool.
  4. A good knock sensor will display a frequency of about 6 to 12 Hz at idle, while a faulty one will have a constant reading.
  5. Replace the knock sensor if the scan tool confirms that it is faulty.
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Troubleshooting and Fixing a Faulty Knock Sensor

Once you have identified a faulty knock sensor, you need to replace it. Here’s how to do it:

  1. Remove the electrical connector from the old knock sensor
  2. Unscrew and remove the old knock sensor from its location
  3. Install the new knock sensor in its place and torque the bolt to the manufacturer’s specification
  4. Reconnect the electrical connector to the new knock sensor
  5. Reassemble the intake manifold and all the components in reverse order of disassembly
  6. Reconnect the car battery and start the engine to verify that the repair has worked.

It’s that simple! You have successfully diagnosed and replaced a faulty knock sensor on your 2000 Subaru Outback.


Q. What causes engine knock in Subaru Outback?

A. Engine knock in Subaru Outback is caused when the fuel ignites prematurely in one or more cylinders, which creates a knocking sound.

Q. Can a faulty knock sensor cause engine damage?

A. Yes, a faulty knock sensor can cause engine damage. It’s essential to fix it immediately to prevent further damage.

Q. Can I drive with a faulty knock sensor?

A. It’s not recommended to drive with a faulty knock sensor. It can lead to decreased fuel economy, reduced engine performance, and potential engine damage.


Diagnosing and fixing a faulty knock sensor in your 2000 Subaru Outback is relatively easy, even for DIY car enthusiasts. Understanding what a knock sensor is, testing it using a multimeter or scan tool, and replacing a faulty sensor is essential for maintaining engine health. By following this comprehensive guide, you can be confident in diagnosing and fixing engine knock on your Subaru Outback safely.

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Joseph Weaver

With a background in engineering and a passion for cars, Joseph brings a unique perspective to our blog. He's particularly interested in the technology and innovation behind Subaru's advanced safety features, and his articles on this topic are always insightful and informative. When he's not writing, he enjoys playing video games and spending time with his family.

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