Fault Code 34: Knock Sensor Issue

[Singasong]

Hi everyone,

This is one of my first posts on this forum but I have been a member for a while and a lot of this information has been very helpful to me. However this one issue I am having I cant seem to find any answers for?

To begin, I have an 1997 r33 Series 2 that is completely stock besides a cat back. The previous owner put an atmospheric BOV which I had changed with haste to the stock one. It has been having crazy fuel consumption issues (getting 200-250kms to a full tank) and blowing a bit of smoke. It also lost power at high rpm when I booted the car, as if the car instantly lost boost and made a rapid fluttering noise out the exhaust. Since changing bits and pieces such as new PCV valve, new valve seals, compression test shows 135 across the board, new spark plugs gapped to 1.1mm and today, a replacement AFM. The smoke has almost completely disappeared and the fluttering noise had gone as well as fuel consumption has been much better (200kms to half a tank). This is where the problem has appeared.

I ran a diagnostic test using the paper clip method only a couple weeks ago and my ecu showed everythign was fine, (code 55). Since replacing the AFM however, I ran another check and the code 34 came up which is my knock sensors. The funny thing is I cant hear any pinging or knocking when im driving and if anything there is a slight noise which is barely audible near the turbo after a good drive when its idling (I dont know if this is considered knocking as I have never heard knocking before, kind of sounds like the heat shield is cooling down or osmething because the knock is very intermittent and doesnt sound at all like marbles in a tin can). I only hear this when the car is idling or on turbo timer and only if i open the bonnet.

When replacing my AFM I was a little pissed off cause my hands are too big and i couldnt reach the one stupid bolt connecting the stock air box which is under the solenoid without risking it falling into the engine bay somewhere so I ended up shoving it in as hard as I could and i suspect i could have accidentally damaged the wiring to the solenoid.

SO my question is, are there any other reasons as to why my ECU could be showing the fault code 34? Could it have been my roughness with the air box and fiddling around that somehow damaged the wiring on something (like the solenoid) that could have confused the ecu into thinking the knock sensors were effed? Or am I kidding myself and it actually is the knock sensor? Ive read that knock sensors need a good thrashing ot actually not work properly, So i dont see how mine all of a sudden "don't work"?

Any suggestions, advice or ideas would be appreciated!

Thanks for your time!

[GTSBoy]

First up, your current fuel consumption is pretty well correct, so no need to keep worrying about that side of it.

Secondly, the loom to the knock sensors is on the other side of the engine from the boost solenoid, so the possibility of you doing anything to the wiring for them is approximately zero.

Thirdly, the noise you hear at idle after a run is stuff cooling down. Knock happens under load. Won't happen at idle 9unless there is some very severe shenanigans going on - far more severe than you need worry about).

The knock sensors (or probably just one of them) may have just chosen this moment to commit suicide. There is a recent thread on the topic of trouble shooting them by bypassing with 500 Ohm resistors that may be worth your time reading.

There is some small possibility that you have damaged the wiring to the boost solenoid and the ECU is confused about what exactly has failed. I just raise this as an extreme outside chance kind of thing, because I can't think of a real method for it to happen besides blaming the impenetrable R33 ECU for things we can't see.

[iruvyouskyrine]

GTSboy, Just for reference, you can run without the knock sensors by replacing them with 470k ohm resistors and watching them out, not 500 ohm.

[GTSBoy]

People just use 470 because that's an available size. The actual target is closer to 500.

[iruvyouskyrine]

Sorry, the point i'm trying to make is that its 470,000 ohm resistors, so 470 Kohm not 500 ohm

[GTSBoy]

Oh, snap. You're right. I might have actually made that same mistake when I posted in the other thread recently. I'll have to check. I actually knew it was kOhm....but I live in a world (at the moment) where I talk to people who drop the kilo off of a lot of units they use. Like they say cal (calories) when they mean kcal (kilocalories) and I fall into their bad habits. I skipped right over your 470 kOhm vs 500 Ohm unit difference!

--edit -- I just checked. I did too. Bastard!

Edited July 26, 2013 by GTSBoy

[iruvyouskyrine]

No worries man, also my first post should read earthing them out not watching.

[Singasong]

Yeah maybe I'm being a paranoid f*** thanks heaps for your contributions. Maybe ill try sorting out the boost solenoid when I get some cash and do a diagnostic test in a bout a month or so, see if the problem still persists. But yeah I thought as much about the cooling down business, the car is definitely not making a knocking noise under load, I guess I'm alright until I hear it ?

[GTSBoy]

No, you can have enough knock to damage an engine without it being audible over all the other noise. If you're very worried, then you should run it up on a dyno with someone who knows what they're listening for (and has the necessary equipment even if it is just a length of hose) to see if there's any knocking.

[simpletool]

Did you use the correct AFM? Off the top of my head the series 1 and 2 are different AFM units. > Series 2 are same as R34.

1. Does it drive fine now?

2. Reset the ECU and re-run the diagnostic. If the knock sensors are stuffed then short them out.

[Singasong]

Hey guys, yeah the afm is definitely the correct one.

I ran another diagnostic test and the code has gone now?

The car runs fine now, idles smooth drives smooth but, besides that, I ran into another problem that's really getting to me. I've searched and searched all over google and forums and stuff and I can't find a decent answer to my specific problem.

As I stated above I've replaced my O2 sensor, AFM, and spark plugs.

Ran a comp test and showed 135 across all 6 cylinders. Ran a smoke test and found one vacuum leak which I sorted which has sort of fixed my loss of power in the high rev range. I have new valve seals as I rebuilt the cylinder head, and I have replaced my old turbo with another second hand turbo ( as I thought it was turbo seals that was te issue)

Now what happens or should I say has always happened is whenever I drive down a hill or something and I press the accelerator a puff of black smoke comes out of te exhuast. This happens intermittently as sometimes the smoke won't come out until I've gone we'll past the hill and come to a stop. Sometimes it will slowly puff out when I'm idling after I've fanged the car or after I've gone down a hill.

My fuel consumption is normal getting about 400kms a tank roughly and my oil level isn't going down so its either burning minuscule amounts of fuel or oil. I don't know. The smoke is black mostly, but I'm not sure if there is tinges of blue in it. But it's definitely not white smoke. Or white-blue smoke.

Now from what I've researched, I've done about 80% of what needs to be done to fix this issue so far.

What I'm wondering is if the crank angle sensor, fuel filter, injectors or fuel pump might have anything to do with the smoke?

Tomorrow I will try out the electrical tape method around the coil packs if they have a split or something.

The reason why this bothers me the most is that my car is stock as a rock, has been since purchase besides a 3" cat back exhaust. Stock r33s shouldn't be blowing smoke like this right ?

Anyway once again any advice or suggestions would be much appreciated! Thanks.

[V28VX37]

Resurrecting old thread because I have a related issue.

I just disconnected the CAS to crank and fill out the oil lines without starting, and needed to clear Code 11 & engine light afterwards.

In addition to Code 11 I also got the following two codes on Nissan DataScan:

• Code 17: ABS-TCS control unit circuit apparently – TCS has never worked since manual conversion, not sure if there's a fix? Luckily ABS does
• Code 34: Knock Sensor circuit

Resetting the ECU cleared 11 and 17 but code 34 reappears each start.

I take it that my knock sensor is dead, or is there possible cause for this? Car is an R34 GTT and moderately modified.

[GTSBoy]

Rub some bacon on it.

[iruvyouskyrine]

Disconnect knock sensors and measure resistance back from knock sensor plug to ECU plug. And measure the resistance of the knock sensors themselves and report back.

[V28VX37]

Disconnect knock sensors and measure resistance back from knock sensor plug to ECU plug. And measure the resistance of the knock sensors themselves and report back.

Thanks I'll look into that.

[V28VX37]

The wiring to the front sensor is damaged, looking to replace it next week.

[V28VX37]

All sorted now. Worth checking those pesky codes every now and then