I've got the P0325 knock sensor code. I separated the connector and read 3.2 volts from the open connector. I put the connector to the knock sensor back together and put a pin into the connector and read 2 volts. Is this the correct voltage readings? I am using a digital volt meter. I pulled the knock sensor and it doesn't appear to have any cracks in the casing. I cleaned the metal surface on the sensor and the block where it attaches. Put it back and cleared the code. Did a couple miles driving and the code reappeared. More tests or replace?

 

Also, the heat shields are rattling at certain rpm's an I need to secure them better. Could they be triggering the knock sensor for some reason?

Edited November 8, 201312 yr by maestro

When you mix vibration and wiring all things seem to become possible but I do not believe the two are related.  I don't know if this is relevant in this case but sometimes when we get a code like that, even though the work has been done, the code still needs to be "cleared".  At this point this could be your issue (13 year old car the computers were less advanced).

 

If not it seems to me that you have done your due diligence I would replace it...there may be a mechanic who posts that has another thing for you to check.

I've got the P0325 knock sensor code. I separated the connector and read 3.2 volts from the open connector. I put the connector to the knock sensor back together and put a pin into the connector and read 2 volts. Is this the correct voltage readings? I am using a digital volt meter. I pulled the knock sensor and it doesn't appear to have any cracks in the casing. I cleaned the metal surface on the sensor and the block where it attaches. Put it back and cleared the code. Did a couple miles driving and the code reappeared. More tests or replace?

 

Also, the heat shields are rattling at certain rpm's an I need to secure them better. Could they be triggering the knock sensor for some reason?

No, rattling heat shields don't trigger the knock sensor. Suggest just keep on driving, if the CEL for knock sensor stays off. Did you clear the code, or remove, and re-install the battery cable after a 5-10 minute wait? Sometimes, no code clearing is necessary, if the knock sensor is working properly. Also, I seem to remember that new knock sensors are available on the cheap on e-bay or Amazon.

+1^ dirt cheap, $15 shipped.

I cleared the code with my actron code reader. Did a search on amazon and yep, $15. I think I'll go ahead and try replacing since it cost way less than I thought it was going to. I'll post whether it works or not.

Voltage isn't the issue at the knock sensor, its the resistance of the sensor element, and the signals that get sent back to the ECU, which can really only be recorded with an O-scope. If you get a code and the wiring isn't chewed up, replace the sensor.

 

Heat shields are easy, get a couple 2-1/4" pipe clamps from the auto parts store and bolt them onto the pipes over top of the heat shields. You may have to remove the bolts on the ends and bend the little "wings" in, but they're a permanent fix for heat shield rattles.

Or you can pop in a 560k ohm resistor to keep her happy, but the ecu will not then be able to retard timing if it does detect spark (but if everything is sound mechanically usually running premium fuel will let you run like this).

 

Right that code _never_ means it is actually detecting knock (there is no indication to the user when it detects knock; it just retards the timing).

Edited November 16, 201312 yr by porcupine73

I'm also getting this code on rare occasions.  I've cleared it but it does recurr.  Hasn't doen it for a few weeks now and it seems to drive the same even when the check engine light comes on.  No other codes appear.

 

This is on a 95 Outback L wagon and they say you have to tear the whole top assembly, intake manifold etc. off to get to it.  Just as soon not do that.

Hi dburton, on yours the knock sensor might be cracked, that was very common on that era. You just need a socket and an extension. I have no idea why the manual says to remove the intake manifold, that is completely unnecessary.

 

I'm also getting this code on rare occasions.  I've cleared it but it does recurr.  Hasn't doen it for a few weeks now and it seems to drive the same even when the check engine light comes on.  No other codes appear.

 

This is on a 95 Outback L wagon and they say you have to tear the whole top assembly, intake manifold etc. off to get to it.  Just as soon not do that.

replace the knock sensor.  it doesn't require removing all that stuff - takes 15 minutes.  yours is even easier than some. 

$15, 15 minutes, done.

 

this issue is so common you're best off just replacing it with new now and being done with it.

file bottom of knock senser and top of block were it bolts up and try it have had many latly that knock senser was not grounding Must be grounded and bolt to very clean surface

The excellent picture above shows what you need but I also did a somewhat educational video about this process last year:

I have seen issues with many cheap knock sensors and usually it's not the sensor itself if it has a removable pigtail.

 

Just a heads up if you have a knock sensor code come back after a few weeks...

Thatnks for all the great replies to this problem!  I wasn't looking forward to tearing off my intake maniforld just to change this thing.

I like to bolt them higher up on top of bell in front of starter makes it a bitt less sensitive and easyer to get to then you can get a bitt more advance outa it

Nitty gritty on knock sensor replacement: http://www.ultimatesubaru.org/forum/topic/116520-knock-sensor-101-and-replacement/

I changed my knock sensor a week ago and have not seen that code since. Like the others say, it is a breeze to change. Just use long extensions and be sure to take note of the orientation of the knock sensor before you remove the old one. Put the new one back in the same way or you risk cracking the new one. However I am still getting the P0420 catalyst error code.

420 pluging cats or exhaust leak