Knock sensor trouble, Code 34.

[IanS]

Im so tired of banging my head against the wall. Ever since I pulled my car out of storage this spring the ECU has been in safe mode. Checking diagnostics reveals code 34. I know Nissans like to chew through knock sensor, so I picked one up, and put it in, problem fixed right?

Not so much, its still throwing code 34, but here is where things get weird. I have all the KS failure symptoms, lagginess between 2K and 3K RPMs, poor fuel economy, and of course, code 34. Normally when a KS fails, at least in my experience if the code is cleared, it will take a little while to re appear, but if I clear my code, then start the car, even for 10 seconds, the code will reappear.

I started running through the troubleshooting in the S14 FSM but my DVOM decided to fail at the perfect moment before I could actually do anything.

In a vane attempt to fix the issue without my multimeter, I grabbed a 1K ohm resistor and stuck it into the knock sensor plug towards the ECU in an attempt to trick the ECU into thinking the sensor was good, but to no avail, I still get code 34 as soon as the engine is started.

This leads me to believe I have a break in the wiring somwhere between the ECU and the Knock sensor sub connector on the Intake manifold, but Im not sure.

I know it is possible to trick the ECU using a resistor, but Im not sure what resistance. I found that people have successfully used a 1K ohm resistor on 300ZX TTs and I was under the impression that both engines used the same knock sensor. Im wondering if they do indeed use the same sensor, but use different knock limits defined by the ECU, hence the 1K would not work. This leads me to my questions.

Any ideas pertaining to the knock sensor issue itself?

Anyone know off hand what resistance is needed to trick the redtop ECU?

[IanS]

Bump, I thought of something else. My KS has two wires on it, and the harness has two wires on it, but the only wiring diagram that I have is for the S14, and it shows a single wire with a ground insulator. What is the second wire for, is it a signal ground, or is it something else. My real question is, do I need it if I re wire the KS completely.

[IanS]

Cmon guys, I need to at least bounce ideas off someone.

[MikeDombeck]

i changed my ks in my ca a while back... it turned out the wiring harness was messed up. i ran a new wire strate from my ks to the ecu.. worked fine after that.

[efrain240sx]

The 2nd wire is just some kind of ground wire. If you connect it to the KS it makes the car run super retarded. I tried it and it wasn't so nice. maybe you're just knocking

[ryan15]

I am actually trying to figure out the same issue, I diagnosed it tonight, also the resistor is suppose to be 1000k,not 1k according to the 300zx knock sensor link.... I am looking to see what the resistance is suppose to be for the knock sensor. I`ll keep you posted.

[IanS]

I am actually trying to figure out the same issue, I diagnosed it tonight, also the resistor is suppose to be 1000k,not 1k according to the 300zx knock sensor link.... I am looking to see what the resistance is suppose to be for the knock sensor. I`ll keep you posted.

Sweet, thanks. I wont have time to dig back into it until Wednesday night, I guess Ill have to swing by radioshack for some more resistors.

[codyace]

Are you postive that you even have a working sensor?

In the FSM there is a troubleshooting procedure on how to test resistance at the knock. Try that first.

I've also seen situations where a knock code becomes hard to remove from the ecu...not sure why tho!

[codyace]

http://forums.maxima.org/showt...ensor

That is a knock guide thing for the Maxima.

They mention a 470k resistor.

[IanS]

Are you postive that you even have a working sensor?

In the FSM there is a troubleshooting procedure on how to test resistance at the knock. Try that first.

I've also seen situations where a knock code becomes hard to remove from the ecu...not sure why tho!

Yes, I did ohm out the knock sensor, it checks out OK, odly enough, the car returned to normal on my way home from work this evening, from the time I left work everything seemed to be running smooth, the AFRs had leaned out slightly, and the flat spot between 2 and 3K was gone, but when I reached the last few stoplights before home I could tell it was back in safe mode.

http://forums.maxima.org/showt...ensor

That is a knock guide thing for the Maxima.

They mention a 470k resistor.

Ive seen 470K tossed around, but the 1000K ohm seemed to be the one that had the best documentation.

[codyace]

Ive seen 470K tossed around, but the 1000K ohm seemed to be the one that had the best documentation.

I can't provide any real time feedback on it, as I've always had K/S disabled on my cars.

I remember some Altima guys a long time ago just relocating it to the firewall (essentially not doing anything) too lol.

You wouldn't happen to have a wacky issue with TPS and or Coolant Temp Sensor would you? Have you repalced the K/S with a known working one? Essentially any mid 90's Nissan has the same one....

[ryan15]

OK heres a little bit of what is going on with mine, hopefully you can use a little bit of my info.

Alright first off for the record, my swap came with a z32 maf and 550cc injectors also a chipped ecu of course, and either the bulb is burnt out or its disabled somehow, so I cant check codes, all I have is my dash light hooked up when I do get CEL.

I am having a tps problem as well, it will only adjust down to .9 volts, I dont have the money to fix it right now, so it could be PART of the problem, but I ruled it out because the problem is intermittent.

Also the FSM is garbage when it says how to tests the KS, it says check for continuity which checked out, but id rather I have a range to work off of, with the connector unplugged I have 550k OHM. I think the KS is on its way out thats why I am having the driveability problems as you described.

Well I hope that helps the least bit.

Ryan

[IanS]

You wouldn't happen to have a wacky issue with TPS and or Coolant Temp Sensor would you? Have you repalced the K/S with a known working one? Essentially any mid 90's Nissan has the same one....

Nope car runs perfect, ets been running essentialy problem free for 4 years now. The only code I have is the knock code. If I reset the ecu and recheck it reads code 55 until I start the car, then 34 comes back. I have the evening off, I brought my good DVOM (fluke) home from work, so I can actually test everything. Im going to try running a new wire all the way from the ECU to the KS.

[codyace]

Runnign a new wire would certainly ensure that is your only issue, but with that said, Nissan knock sensors are known to fail at random, and cause issues from the get go. My Maxima was doing the same thing (i'd reset it with my computer, and it would come right back). I put another k/s on it (from a 1.6 sentra or somethign at a junkyard) and it's been fine now for the past 4 months.

[efrain240sx]

I can't provide any real time feedback on it, as I've always had K/S disabled on my cars.

I remember some Altima guys a long time ago just relocating it to the firewall (essentially not doing anything) too lol.

You wouldn't happen to have a wacky issue with TPS and or Coolant Temp Sensor would you? Have you repalced the K/S with a known working one? Essentially any mid 90's Nissan has the same one....

Hey codyace how did you disable you're K/S ? Did you relocated to a different area, or did you remove it and jump it with a resister, or did you just remove it from the car and erased the K/S feature of the ECU ? Thanks

[efrain240sx]

BUMP I want to know how codyace disabled his K/S

[IanS]

Well I got mine figured out. The wiring was bad, in two places. After doing some testing, I discovered that there was no continuity from the intake manifold plug, down to the knock sensor. I used some test leads to hard wire the KS to the wiring harness before the manifold.

Thinking it was fixed, I fired it up and then checked for codes, but alas, still code 34.

With the ECU plug off, I probed the KS wire, no continuity between the ECU and the plug near the manifold, uh oh, wiring gremlins.

On a whim I started unsheathing the harness near the ECU, only to find a single open wire, not but 6" from the ECU.

With the wire repaired and the KS still hardwired in I gave her one last go, SUCCESS, code 55. The car drives so much better, and its a good thing too, she goes on the dyno tomorrow afternoon.

The moral of the story? Good multimeters, are worth the dough.

[codyace]

The moral of the story? Good multimeters, are worth the dough.

You betcha! I love my fluke!

Good to hear you got it sorted out! Damn us and our 10 year old Nissans hehe.

TO the guy who asked abotu disabling K/S: I get them turned off on the wolf ecu's....

[IanS]

Well I just got back from the dyno, I made 251.4 RWHP, with 250 RWTorque. Im very please with these results, Im going to scan all my graphs tomorrow, then I will make a new thread.