DIY: Subaru Knock Sensor Replacement

Difficulty Level

Tools/Supplies Needed:

• multimeter
• 12mm 3/8" driver socket
• 3/8" drive 3" and 6" extension
• 3/8" ratchet
• torque wrench
• OBD2 code reader

Procedure:

• the knock sensor is located under the throttle body on the driver's side of the vehicle on top of the engine block
• disconnect the wiring harness going to the knock sensor by depressing the tab on the plug and pulling straight out
• using a 12mm socket, along with a 3" and 6" extension, you can access the bolt easily and remove it
• once the bolt is removed, now the knock sensor itself can be removed
• clean the surface of where the sensor is bolted to, to ensure it has a good ground
• install the new sensor making sure it is at a 60 degree angle in accordance with the rear of the engine
• reinstall the bold and tighten it to 24nm or 17.4ft lbs
• reinstall the wiring harness ensuring it isn't rubbing on anything
• clear engine code either by disconnecting the battery or using an OBD2 code reader
• start the engine to ensure it is operating correctly

Video tutorial on how to replace the knock sensor on a Subaru. A faulty knock sensor will typically cause poor fuel mileage, decrease in power, flat spots in the throttle, throttle hesitation, and hard starting. This particular video was done on a 1999 Subaru Forester with a 2.5L 4 cylinder.