After 2 years of owning this car, I finally found the diagnostic connectors under the dash. I installed a d/t d/p toggle switch so I can access the codes without taking off the lower panel. I get a code 22 on U check but nothing in D check mode. I checked my repair manual and it states that the intake manifold needs to be removed to replace the Knock sensor. Is this correct? The car runs great @ 172000 miles but I see that alot of people on this site say there is a problem with them. I love this car and plan to run it until the wheels fall off. Thanks, Keith

The knock sensors on the early legacys are known for failing due to a defect. Everytime my engine gets any kind of wet it throws up that code. I let it dry out and then reset it...because I am too lazy to replace it.

You can replace it without removing the manifold! A 10 inch extension on your socket driver should be enough. The hard part is disconnecting the wire and connecting it again..

 

Don't tighten the new sensor too hard. Just use a "firm hand" and stop when you feel resistance to further rotation. Kinda like spark plugs.

Agreed with Setright.

 

Just make sure the sensor you're getting has a white connector instead of the grey connector your old one has. The white connector means it's the updated one, SOA realized the old ones were prone to cracking and issued a new-and-improved one.

 

www.subaruparts.com should have them for like $30...

Thanks to everyone that replied. I see now that it is accessable without removing the manifold. 1 more question. I still have a code 22. My repair manual states that to check the knock sensor. check the resistance to ground and there should be none. I get no continuity at all. I can see that the plastic is cracked on the top of the sensor. should I replace it? Thanks, Keith

Really, if you have the grey connector, you should replace it regardless. If yours is cracked (which doesn't surprise me), then you should definitely replace it. The white one is updated to be more resistant to cracking, and is also not oversensitive as the grey one is.

 

Make sure when you change it that you have a long magnet grabber/reacher thingy, as you will most likely drop the bolt down on the block where you can't reach it any other way.