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Old 09-09-2021, 12:46 PM   #1
reidsedan
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Member#: 503157
Join Date: Jun 2019
Location: Ontario, Canada
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2008 WRX sedan
WR Blue

Default CEL of High voltage from knock sensor

Recently replaced my old knock sensor on my cobb stage 2 ots 2008 WRX. Reason being that it was giving me false knock readings at random occasions after shifting and accelerating. I got it tested and looked at by a tuner and was confirmed that this was a false knock and not real, besides the fact that I have never heard any sign of actual knock or the side effects from it (besides the feedback knock reading and according DAM alteration). Replaced the sensor and after inspecting the old sensor I can confirm it had a crack in it, did tests with a voltmeter on it too and confirmed its not reading actual feedback properly. After replacing, started the car and instantly I notice a CEL (P0328), Knock Sensor 1 Circuit High Input. Also noticed the DAM is at .500. Tried driving it around and hoped the DAM would go back to normal and maybe I could try clearing the code after I got back, but instead what was happening was the feedback knock would constantly be picking up -5 whenever I was accelerating. This was not the case before I replaced it, the issue was more random and a sign of a faulty sensor. Anyways, after returning home from the drive, I pulled out the sensor, cleared the code, started the car without a knock sensor connected, the code was still there (high voltage input). Then I tried connecting the old sensor in hopes I could at least clear the code, but after clearing the code and restarting ECU, code was still there. After this, I disconnected the sensor again, checked continuity between the sensor connector and main engine harness and it appears to be a stable connection. Checked voltage output of the sensor itself with the voltmeter by actually "knocking" the sensor by hitting it with a screwdriver and the voltage output read as it should (a couple volts I believe). Reconnected the new knock sensor, cleared code once again, code still there. Just yesterday however, I had a glimmer of hope when I was driving for about 15 minutes and all of a sudden I notice my DAM go back to normal at 1.000, and I also notice my feedback knock is not constantly reading -5 when I'm accelerating. I was hoping maybe this was a sign that if I tried clearing my code once again, it would go away for good. Unfortunately after clearing the code and restarting ECU it was still there. I tried driving around once again and was noticing the -5 feedback reading is now sporratic, not the same type of sporratic like it was with my old sensor, but almost appears in clumps of time, like for 5 minutes of driving the feedback will be at -5 whenever I accel, and for the next 10 minutes it will be gone, then for 2 minutes it will appear again. One thing also is that the feedback knock is never any other reading besides -5 which is not natural. I am hoping for some sort of clarity or any other ideas that may help with my situation to get my high voltage code cleared and my newly replaced knock sensor to start behaving as it should. Thanks.
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Old 09-10-2021, 08:57 PM   #2
Haevn
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did you torque it down to spec and is it at the proper angle?
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Old 09-11-2021, 01:02 AM   #3
AliBenn
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Wow
Great diagnostic info
Great freakin job

3 Qs
-only P0328? No other codes?
-sorry, got to ask, you got the correct side bank?

https://www.engine-codes.com/p0328_subaru.html

-the sensor reads cam(s) or just engine vibration?
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Old 09-11-2021, 01:09 AM   #4
AliBenn
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Old 09-11-2021, 01:09 AM   #5
reidsedan
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Quote:
Originally Posted by Haevn View Post
did you torque it down to spec and is it at the proper angle?
Didnt know there was info on that, I put it back in the way I remembered the old sensor was, and torqued it to a typical tightness i guess, not sure exactly how many foot pounds, not too tight of course.
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Old 09-11-2021, 01:12 AM   #6
reidsedan
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Member#: 503157
Join Date: Jun 2019
Location: Ontario, Canada
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2008 WRX sedan
WR Blue

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Quote:
Originally Posted by AliBenn View Post
Wow
Great diagnostic info
Great freakin job

3 Qs
-only P0328? No other codes?
-sorry, got to ask, you got the correct side bank?

https://www.engine-codes.com/p0328_subaru.html

-the sensor reads cam(s) or just engine vibration?
P0328 only. The sensor is meant to read knocking from the block.
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Old 09-11-2021, 04:29 PM   #7
AliBenn
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1998 /2005 STunIcorn
Acadia Green RS-T

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Bc there are 2 banks and (potentially) 2 different codes
Try replacing the opposite side sensor?
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Old 09-11-2021, 04:41 PM   #8
reidsedan
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Join Date: Jun 2019
Location: Ontario, Canada
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2008 WRX sedan
WR Blue

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Quote:
Originally Posted by AliBenn View Post
Bc there are 2 banks and (potentially) 2 different codes
Try replacing the opposite side sensor?
There's only 1 sensor. (not sure why there would be more than 1)

Last edited by reidsedan; 09-11-2021 at 10:12 PM.
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