Knock sensor/ECU has me in a RAGE!
07-28-2011, 07:00 PM
#1
Knock sensor/ECU has me in a RAGE!
To start this off ive read probably almost every thread online that has to do with 4th gen knock sensors.
That said here we go.
I scanned my codes and got a p0325 (Knock Sensor Bank 1) on my handy actron obdII scanner. I go ahead and replace the knock sensor. Reset the ecu, code cleared....fine. I scan after a week and its back. I clean contacts on the knock sensor, LIM and the front grounds on the UIM for the wiring harness. I clear codes again and they clear. After a few days theyre back. O and i have been using 93 octane all the while btw...anywho i loosen it and make sure when i tighten it its not too loose or tight....try resetting the code and it wont clear at all....Ive tried clearing it with the scanner 83941234 times...also tried clearing the codes by pulling the battery and using the self diagnostic screw on the ecu....nothing always the damn P0325....Im sure the KS and subharness are good but what would make the code "Stuck" in the ECU like that? And why does it keep returning.....any ideas.....anyone else like this?
BTW car is a 95 3.0 5MT
Im thinking of trying the resistor test but at this point without the ECU clearing how would that help?
That said here we go.
I scanned my codes and got a p0325 (Knock Sensor Bank 1) on my handy actron obdII scanner. I go ahead and replace the knock sensor. Reset the ecu, code cleared....fine. I scan after a week and its back. I clean contacts on the knock sensor, LIM and the front grounds on the UIM for the wiring harness. I clear codes again and they clear. After a few days theyre back. O and i have been using 93 octane all the while btw...anywho i loosen it and make sure when i tighten it its not too loose or tight....try resetting the code and it wont clear at all....Ive tried clearing it with the scanner 83941234 times...also tried clearing the codes by pulling the battery and using the self diagnostic screw on the ecu....nothing always the damn P0325....Im sure the KS and subharness are good but what would make the code "Stuck" in the ECU like that? And why does it keep returning.....any ideas.....anyone else like this?
BTW car is a 95 3.0 5MT
Im thinking of trying the resistor test but at this point without the ECU clearing how would that help?
Last edited by Boothers96; 07-28-2011 at 07:02 PM.
07-28-2011, 07:58 PM
#3
The very first time i scanned was because the CEL was on because when i was cleaning my MAF and went to put my K&N back on and one of the wires for the intake air tamp sensor broke so i replaced it and that code went away.....we all know that the KS code itself will not trigger a CEL...but since fixing the IATS, the only code im pulling is the KS code P0325.
07-28-2011, 08:08 PM
#5
07-29-2011, 09:06 PM
#8
I know exactly how he fells and I have gone through the same process. I eventually ponied up and bought an OEM knock sensor this week. It was off for a few days and it came back. Its the only code I have and I am reading 525K ohms through the harness which is within spec. My question is that some people say to replace the harness but its only "1 wire" but when I examine the harness, its one wire at the knock sensor itself and at the other end of the harness, its two wires. Where does the second wire go??
07-29-2011, 09:24 PM
#9
I know exactly how he fells and I have gone through the same process. I eventually ponied up and bought an OEM knock sensor this week. It was off for a few days and it came back. Its the only code I have and I am reading 525K ohms through the harness which is within spec. My question is that some people say to replace the harness but its only "1 wire" but when I examine the harness, its one wire at the knock sensor itself and at the other end of the harness, its two wires. Where does the second wire go??
08-01-2011, 07:44 AM
#10
Exactly...mine is the same...at the wiring harness the plug on both sides (wiring harness side and subharness side) has 2 wires....at the KS connector side it only has the one wire...i was going to get another subharness thinking it had broken but idk...anyone with a properly functioning KS and sub harness could take a look quick and let us know?
08-01-2011, 07:53 AM
#11
The one wire is definitely a shield. Look at the diagram for the knock sensor wiring in the EC FSM section.
The voltage from a piezo element is very small. The signal need to be protected from noise until it can be amplified in the ECU.
That reminds me, make sure that the spot on the block that the knock sensor bolts to is free from oxidation. The knock sensor is grounded through the mounting point on the block.
The voltage from a piezo element is very small. The signal need to be protected from noise until it can be amplified in the ECU.
That reminds me, make sure that the spot on the block that the knock sensor bolts to is free from oxidation. The knock sensor is grounded through the mounting point on the block.
08-02-2011, 02:18 AM
#12
The one wire is definitely a shield. Look at the diagram for the knock sensor wiring in the EC FSM section.
The voltage from a piezo element is very small. The signal need to be protected from noise until it can be amplified in the ECU.
That reminds me, make sure that the spot on the block that the knock sensor bolts to is free from oxidation. The knock sensor is grounded through the mounting point on the block.
The voltage from a piezo element is very small. The signal need to be protected from noise until it can be amplified in the ECU.
That reminds me, make sure that the spot on the block that the knock sensor bolts to is free from oxidation. The knock sensor is grounded through the mounting point on the block.
08-02-2011, 03:45 PM
#14
!!! I will have to check for continuity from the ECU to the harness but I am trying to avoid touching that harness. It has never been disconnected or removed for any reason. I am starting to wonder if it is not going away because it may be detecting a fault...out of ideas.
05-25-2012, 09:03 AM
#16
Reviving this thread to follow-up. When I turn the key to ON, and measure voltage through harness, it shows 0v. Can someone tell me the color of the wire going back to ECU? I am trying to locate at back left corner of engine instead of going directly to ECU since I know it was never touched.
05-25-2012, 02:27 PM
#18
05-25-2012, 02:39 PM
#19
I'm having the same issue as the OP, only difference is mine will clear, car will drive fine, then after a few starts I'd get a hard start and slight bogging between shifts and power is gone. I'm also getting p1400 and p1401 as well as p0325. Anyone have any ideas of what it might be? I've already swapped out the is with an oem one, along with the subharness,but to no avail.
05-25-2012, 04:04 PM
#21
I am going to have to remove the ECU harness and see if 5V is coming out of pin 64. Went and tried several of my friends cars and they have 5V at the harness...mine has 0v with key in On position.
05-26-2012, 05:18 PM
#24
Did some digginu up and I found this clause from Daniel B. Martin:
"The resistance specification between pin #2 and ground is the only one I found in the factory service manual.
My (admittedly incomplete) understanding of the Knock Sensor is that it contains a piezoelectric crystal which generates a voltage when subjected to physical shock. As such, it amounts to a special-purpose microphone which "listens" for engine knock. Therefore it is a different kind of sensor than the type which has a wire winding with a measurable resistance.
Pin #1 is not part of the KS signal circuit. It is only the outer shield of a coaxial cable. Consequently I would expect an open circuit between pins #1 and #2. Anything else would compromise the signal from the KS to the Engine Control Module."
After seeing this, I went and test for continuity between pin 1 and 2 of the harness and it is showing continuity. Will start splicing open the harness and getting rid of that black substance stuck to the wires...not sure why Nissan put it there.
"The resistance specification between pin #2 and ground is the only one I found in the factory service manual.
My (admittedly incomplete) understanding of the Knock Sensor is that it contains a piezoelectric crystal which generates a voltage when subjected to physical shock. As such, it amounts to a special-purpose microphone which "listens" for engine knock. Therefore it is a different kind of sensor than the type which has a wire winding with a measurable resistance.
Pin #1 is not part of the KS signal circuit. It is only the outer shield of a coaxial cable. Consequently I would expect an open circuit between pins #1 and #2. Anything else would compromise the signal from the KS to the Engine Control Module."
After seeing this, I went and test for continuity between pin 1 and 2 of the harness and it is showing continuity. Will start splicing open the harness and getting rid of that black substance stuck to the wires...not sure why Nissan put it there.
05-26-2012, 09:24 PM
#25
I believe from time to time people replace the ks harness as well. It should probably be replaced since there is not supposed to be continuity there.
Edit:If the ecu doesn't detect the knock sensor ohms it throws the code.
If it detects knock from the sensor it throws the code.
If there is interference in the wire (detecting a false signal) it will throw the code.
Edit:If the ecu doesn't detect the knock sensor ohms it throws the code.
If it detects knock from the sensor it throws the code.
If there is interference in the wire (detecting a false signal) it will throw the code.
Last edited by maxgtr2000; 05-26-2012 at 09:30 PM.
05-27-2012, 07:26 AM
#26
I believe from time to time people replace the ks harness as well. It should probably be replaced since there is not supposed to be continuity there.
Edit:If the ecu doesn't detect the knock sensor ohms it throws the code.
If it detects knock from the sensor it throws the code.
If there is interference in the wire (detecting a false signal) it will throw the code.
Edit:If the ecu doesn't detect the knock sensor ohms it throws the code.
If it detects knock from the sensor it throws the code.
If there is interference in the wire (detecting a false signal) it will throw the code.
11-29-2012, 11:30 AM
#28
This is not true, The KS regularly detects knocking and the ECU adjusts timing accordingly. It will not trigger a code for typical knocking.
12-01-2012, 04:24 PM
#29
Junior Member
Join Date: Sep 2012
Posts: 29
i replaced the KS on my 96. the DTC cannot be cleared until the problem is fixed. It is not like other codes the activate the check engire light for some reason. Until i could get the sensor, i did the resistor trick (radio shack 460k Ohm) and bypassed the sensor in the female part of the harness where the KS sub-harness connects. Cleared the code and it worked like a charm so i could pass state inspection. then when the KS was ordered and arrived i put it in and havent had a problem since. I highly recommend spending the dollar for the resistor to determine if the sensor/harness is at fault. Otherwise, you'll be throwing parts after a problem without knowing the real solution. BTW, dealer part is way more expensive than aftermarket.
12-04-2012, 01:49 PM
#31
Junior Member
Join Date: Apr 2011
Location: Saint Charles, IL
Posts: 47
I just popped a 470k ohm resistor in there- the code did not go away. It's literally the only code I have, and won't go away with the ECU reset screw, OBD II scanner, or disconnecting the battery. It also returns without starting the vehicle.
12-16-2012, 01:09 PM
#32
Junior Member
Join Date: Sep 2012
Posts: 29
that is very strange. the only other thing it can be is an open circuit between the harness and the ECU. Might want to trace the circuit and test for continuity from the harness end to the ECU. Just checking, you placed the resistor across the harness that the KS plugs into and stil get the code? This is a foolproof temporary fix. Must be the wiring back to the ECU.
08-21-2013, 09:42 PM
#34
Sorry to bump this thread up, but I am now inquiring about this myself, as I have replaced the subharness twice already, and the knock sensor twice as well... Bought the one from autozone and an original one from the junkyard that was in working order. I reset the ECU 5 times, and it pops up without even having to turn the car on. I'm stumped on this and would like some input.
Tomorrow I will try to get an extra ECU from the junkyard and see if that helps. I'm wondering if this would trigger the code, which is that I have a TechnoSquare ECU, and it originally came with a bad core, that is, that it always had that knock sensor code from the beginning and it seems to have transferred out to my original one now.
Should I just start to splice into the main harness and remove the wire that is causing the code to become tripped? Or should I check pins on the ECU and measure for continuity between the harness and ECU? If so, how would I do that, since the FSM seems a bit confusing when reading it
Thanks everyone!
Oh, FYI, it's the only code I'm getting at the moment.
Tomorrow I will try to get an extra ECU from the junkyard and see if that helps. I'm wondering if this would trigger the code, which is that I have a TechnoSquare ECU, and it originally came with a bad core, that is, that it always had that knock sensor code from the beginning and it seems to have transferred out to my original one now.
Should I just start to splice into the main harness and remove the wire that is causing the code to become tripped? Or should I check pins on the ECU and measure for continuity between the harness and ECU? If so, how would I do that, since the FSM seems a bit confusing when reading it
Thanks everyone!
Oh, FYI, it's the only code I'm getting at the moment.
08-22-2013, 09:36 AM
#37
I haven't cleaned the grounds, per se, but I did re-wrap them in electrical tape due to them being a bit exposed. I'll try that in a bit and see if it helps since I have some free time before work.
And already got the fsm downloaded onto my laptop, phone and tablet. Lol. I'm just a bit skeptical about probing the electrical with the car on/off and the power running. But I guess I have to give it a shot.
DragOn97.... How is your comment helpful?
And already got the fsm downloaded onto my laptop, phone and tablet. Lol. I'm just a bit skeptical about probing the electrical with the car on/off and the power running. But I guess I have to give it a shot.
DragOn97.... How is your comment helpful?
08-22-2013, 10:12 AM
#38
Newbie - Just Registered
Join Date: Sep 2012
Posts: 1
I just fixed the same issue with my 96 SE. I tried the resistor trick as well and it intermittently worked, I measured for voltage at the harness connector and had 5 volts. The problem kept randomly coming back and it ended up being an intermittent short in the harness between the KS and the ECU. I just rewired that circuit and the problem is fixed. The car runs great and no more KS code. This is my daily driver beater so trying to find out exactly where the short is was of no importance to me, I just bypassed the entire wire. I ran the new wire from the KS sub harness all the way to the ECU. The wire I used was speaker wire as it appears Nissan used something similar to that originally, just make sure to solder the connections and heat shrink the area for a reliable repair. Hope this helps.
Justin
Justin
08-22-2013, 06:05 PM
#39
I'm thinking about just doing that soon. I swapped ECUs to see if that was the problem but the code kept coming up. When you did rewire (and yeah, it does look like speaker wire though Nissan said it was white... lol) did you ground it out to the main harness or by the manifold grounds? I ask because I stripped the wire from the subharness connection back and noticed it was sort of "tapped" into with a ground. Or did you just wire it straight from the subharness to the ecu without a ground? Thank you for your reply Justin
- Axel
- Axel
09-01-2013, 11:45 AM
#40
Junior Member
Join Date: Apr 2011
Location: Saint Charles, IL
Posts: 47
I just ran a piece of speaker wire from the ECM to just before the KS sub-harness, and was able to delete the code immediately. Apparently there was a short in that wire somewhere, so I was still getting continuity but likely getting a bad signal from the KS.
Thanks dude. Hopefully others with this problem also see your post. I've been chasing this forever.