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CEL Knock sensor malfunction P0325


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13 replies to this topic

#1 terryb52

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Posted 12 July 2008 - 10:25 PM

OK-- how quickly do I need to do anything? I was in hot traffic on Thursday, more driving across town than I usually do and the CEL came on. Code said knock sensor. The next day no light. No light today either. Can I wait to do anything? See if the light comes back on? Estimate about $190 here in colorado springs. I just put in a new starter last month and a swapped engine in Feb. so I have about $2300 into this car over the past few months and don't want to spend more until I have to! I will be driving across country in Sept. and want to know if that is something I should plan on taking care of before the trip???

Thanks.

#2 McDave

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Posted 12 July 2008 - 10:36 PM

What are we working on? Do you hear any pinging or knocking?

#3 aircraft engineer

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Posted 12 July 2008 - 10:51 PM

how fast - depends - IF it "is" bad, the timing will retard until the knock goes away - which just eats gas.

My 97 Imp developed a CEL developing on DECEL off the freeway (and there ain't NO WAY IT WILL KNOCK ON DECEL - knock is a "loaded engine preignition" thing) - so I just got tired of the whole thing and RELOCATED the knock sensor.

The 2.2 has it right under the intake manifold at the back - easy access to the 12mm head bolt. Pull the battery cable, disconnect the wire connector and go in and unscrew it (long extension, short socket - IF you want to put a new one back in where you took the old one out, pull the airbox out for access - otherwise don't bother)

I relocated it to the flange to the trans (auto) where a "convenient bolt hole" just happened to be (drivers side). Problem is apparently gone

The knock sensor gets brittle after it gets old and it also gets "sensitive" - or so it seems. Relocating the sensor will make it "ineffective" at sensing a knock, but if a knock isn't loud enough to hear, it isn't "bad" enough to do damage.

The "key" is that it PASSES THE EMISSIONS TEST (which is the ONLY reason I was concerned about the light anyway)

Sensor is $75 or so on line for the older ones, plus maybe 2 hours MAX to swap it (and that's for a non-mechanic - start to finish) The hardest part will be reaching in and starting the bolt into the top of the block since you have to work by feel

#4 grossgary

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Posted 12 July 2008 - 10:52 PM

in general no the knock sensor code won't cause significant problems. but then again if you're going to eventually replace (which you should, it's only going to get worse) then do it now. it's a part that's going to last the life of the vehicle, so do it now and get as much out of it as you can.

that's probably one of the most common failure items on EJ engines, so i wouldn't worry about it too much in terms of a failure item. the rubber material breaks down and cracks.

someone mentioned that they removed it - filled the cracks in with RTV sealant and reinstalled and the code never came back. not a bad idea and it's free (well $2 tube of sealant). and it's really easy to replace too.

they are really easy to do yourself if yo'ure so inclined. no special tools and about 20 minutes tops.

should be replaced with new - not used.

#5 terryb52

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Posted 13 July 2008 - 12:15 AM

I forgot to update my sube info--- I sold my '92 turbo and now have a '98 OB (long story, wish i had my turbo). I don't do any work myself-- all at the shop. I plan on keeping this one at least 6 years unless something else BIG happens. I think the engine is really loud (I had the engine replaced because of rod knock) but have had 3 different mechanics test drive it and they all say it is rattling from the heat shield or an exhaust rattle up front. I think it sounds loud but i might be paranoid. Could that noise freak out the sensor? How do I really know what is doing it? And does malfunction mean the sensor or what it is sensing? ie: do I replace the sensor or do I look for something else?

#6 grossgary

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Posted 13 July 2008 - 05:48 AM

but have had 3 different mechanics test drive it and they all say it is rattling from the heat shield or an exhaust rattle up front. I think it sounds loud but i might be paranoid. Could that noise freak out the sensor?

no that noise is not freaking out the sensor. have the heat shields repaired if it's bothering you - and yes those can be very loud and annoying. some 50 cent hose clamps will likely take care of them for quite awhile and take about 10 minutes (being very generous here with time!) to install.

How do I really know what is doing it?

i've already told you!

that's probably one of the most common failure items on EJ engines, so i wouldn't worry about it too much in terms of a failure item. the rubber material breaks down and cracks.


And does malfunction mean the sensor or what it is sensing? ie: do I replace the sensor or do I look for something else?

that was already answered as well - your knock sensor is failing. you need a new knock sensor. read the rubber material comment earlier.

the sensor needs replaced for your Check Engine Light to go away.

#7 McDave

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Posted 13 July 2008 - 07:36 AM

:headbang: :headbang: :headbang: :grin:

#8 terryb52

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Posted 13 July 2008 - 12:03 PM

OK, OK! No need to chastise me. The light did go off, that's why I asked. I also got 3 different opinions from 3 different mechanics. From add 44k to replace sensor. I will opt for replacing sensor and be done with it!

Thanks for all the advice.

#9 grossgary

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Posted 13 July 2008 - 12:45 PM

OK, OK! No need to chastise me.

i didn't mean it like that. just letting you know i'm not guessing or "think it might be". to an extent there's always guess work but this is based on significant experience and you don't know that. you should question advice...based on some you've gotten particularly!

I also got 3 different opinions from 3 different mechanics. From add 44k to replace sensor. I will opt for replacing sensor and be done with it!

that's common for the check engine light to come and go. they have thresholds (3 out of limits per 10 cycles...or something like that) and it's only meeting that occassoinally. it'll get worse with time most likely.

\I also got 3 different opinions from 3 different mechanics. From add 44k to replace sensor. I will opt for replacing sensor and be done with it!

the best advice you can get will be from people that know those vehicles, makes and the actual engine or sensors you're having problems with. the USMB can arguably outperform any shop in terms of subaru maintenance, repairs, and knowledge. that's a very weighty thing to say - but it's probably true.

#10 four-fleet-feet

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Posted 13 July 2008 - 01:47 PM

OK-- how quickly do I need to do anything? I was in hot traffic on Thursday, more driving across town than I usually do and the CEL came on.

How quickly you need to fix this is up to your personal annoyance threshold.

I had my car nearly 6 months before my knock sensor code popped up. It didn't happen until I was in Arizona and driving cross-town in 105 heat. Then it became a daily thing - light was off on startup if it was under 100, then it would pop on as I either tried to get onto the freeway or leaving a light if I idled longer than usual at a traffic light.

It wouldn't come on in cooler weather (think 80 :eek: here, that is cool in summer Arizona), even if I was on the freeway going full tilt. It also wouldn't come on if the humidity was high (for Arizona, that's about 40%, and only in monsoon season).

When it was off I could sail around town with the AC on full blast and get 25+ a gallon; as soon as it came on I could watch the gas needle dip with every mile. So, it's a tossup whether you get tired of paying for more gas or get really tired of not having power to get around on the freeways. I could barely get Dragon up to 50, let alone 65, the Phoenix in-town speed limit.

Get a real Subaru sensor; aftermarkets don't work as well, and you don't want to do this twice, do you? This is one part where stealerships or online Subie parts sellers are your only options.

Don't want to pay a stealer for the work? Get the part yourself, and then search how to do a knock sensor on this board. Print it out, and any competent mechanic can do it for you - and probably for quite a bit less!

Make sure you trace the wiring into it at the same time, as well - maybe a mouse had a snack on the harness.

#11 McDave

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Posted 13 July 2008 - 02:36 PM

Make sure you trace the wiring into it at the same time, as well - maybe a mouse had a snack on the harness.


Mouse, rat, river rat, squirrel, ground squirrel... I'm not sure which but every spring we get a couple cars towed in with chewed up harnesses.

Tip: Bounce Dryer Sheets contain the same active ingredient as what garbage dumps use to ward off rodents. Just tape a few to the harnesses after making repairs. We've had no recurrences since doing this.

#12 Olnick

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Posted 13 July 2008 - 02:43 PM

Tip: Bounce Dryer Sheets contain the same active ingredient as what garbage dumps use to ward off rodents. Just tape a few to the harnesses after making repairs. We've had no recurrences since doing this.


It's amazing what you can learn on this board! Thanks McDave, nice tip.

#13 terryb52

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Posted 13 July 2008 - 11:27 PM

Thanks again. Heat does seem to be a factor. I will be taking it to a Japanese repair place that fixed my starter and did valve cover gaskets on my '92 turbo. Haven't noticed gas use but haven't driven very far either. That would definately be a factor in a trip to IL from CO. Going in Sept. but it was 95 last year in Oct out there.

#14 screwbaru2

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Posted 14 July 2008 - 05:36 AM

This knock sensor code shows OK to drive on my scanner with is more than the small scanners that go for $200.00. I'd wait until you were ready to replace it, it's not going to hurt your motor. The code means that there is a problem with the system not that the engine is knocking. Happy motoring!




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