Which knock sensor to buy?

[Stevo F]

My '98 Legacy with EJ22 engine is pretty regular throwing a P0325 code for knock sensor. Any recommendations good brand of knock sensor to buy? Also, what is the best way to replace it without removing the intake manifold, since it looks pretty hard to get to?

[FerGloyale]

Easy to get to with a long extension.

Personaly, I would buy OE Japanese made only.  Might not need to be from dealer but should be Japanese made.  "Unisia" I think is the OE maker.

[wtdash]

I've read that the cheaper versions are OK, too.

Just need a long extension and 12mm(?) socket.  Note its orientation when removing to install same.

 

And if there's been any work done on the car around the KS area, it could be unplugged or damaged wiring....and be careful with those wires as they are 20+ years old and getting brittle.

 

p.s. ...the '95 and older were known to crack, but was supposedly fixed on newer models.....so a used one will work too. A KS from a 2.5/EJ25D should work too.

Edited June 24, 2019 by wtdash

[Stevo F]

Thank you everyone. I looked up Unisia and found the right one for my '98- about $45 from Amazon. More pricy than the typical Ebay units but far less than if I purchased form Subaru.

When i removed the old one, I compared the two and they have the identical part #, so the Unisia Jens is true OEM.

The trickiest part was getting it to line up with the hole and getting the bolt started. I could barely get two fingers on the bolt head, but eventually I got it. When I started it up,m it cleatred the CEL on its own and didn't come back on a couple mile drive, so hopefully good to go.

[wtdash]

For future reference and others...you can put some tape (or similar)  on the bolt head to get it to stick / wedge into the socket to hold it. Then use an extension to reach down and reinstall the bolt. Once it's snug the socket should release. 

Just be extra careful not to cross-thread it!

There's probably an even better way that Mech's know. :-)

Edited June 29, 2019 by wtdash

[Stevo F]

I didn’t think of the tape on the bolt head idea this time, but that worked great putting in a hard to get to bolt when installing the Grimmspeed master cylinder brace in my Forester 

[TurboRev]

I recommend the OEM Subaru sensor. I don't mess with aftermarket parts. Search with your VIN on https://www.subarupartsdeal.com/  for the sensor. Hope this helps. 

[1197sts]

I've had no problems with the cheapo's that you can get on ebay. Sometimes its hard to determine which connector it has, there are two common connector styles, but it has just one wire going to the sensor so just splice your original connector onto the new sensor if needed and it works fine. I only deal with the NA engines, might be more critical on turbo models.

Edited November 14, 2019 by 1197sts

[wtdash]

You can also swap from one style to another -there's a little tab on each where the wire is held in place. Depress the tab and remove the wire on both and swap....or @ least I did. :-)

[GeneralDisorder]

Cheap knock sensors are a REALLY bad idea. Just because the sensor meets the ECU's expectations of circuit resistance says NOTHING about it's ability to accurately profile the noise from the engine and trigger the ECU's knock detection threshold correctly. The sensor is a piezoelectric microphone and buying the cheap ebay ones is the equivalent of buying dollar store earbuds and trying to listen to high definition audio. The accuracy of the sensor depends on MUCH more than the resistance of the circuit used by the ECU to determine if it's failed or not. 

They are also "tuned" to listen to specific kilohertz frequency ranges. Anything from about 2Khz to 17Khz can be found on different engines and the determining factor on knock sensor frequency is largely the bore and stroke of the engine. So for reasons of accurate knock detection it is a bad idea to give the ECU a different model of sensor other than what it was designed to listen to. 

GD

Edited November 14, 2019 by GeneralDisorder