cbh148

My s13 has a redtop SR swap that was previously in a RHD s14 track car and who knows what all else before that. It came with a fatty o2 sensor installed, but I swapped in a skinny o2 sensor from my buddy's used parts bin because I thought it was the right thing to do since I have a 62 ECU.

I recently got a Consult cable and ECUtalk software plus OBD Scantech (trial) software. According to ECUtalk, my o2 sensor has zero voltage. However, it says my friend Scott's redtop SR does have a voltage reading (62 ECU and skinny o2 as well). I tested another friend's SR, but it's an s14 SR with a fatty o2 sensor, so I assume that that's why it displayed the typical voltage cycling that most oxygen sensors do.

I thought my gas mileage got a little better when I switched to the skinny o2, but I wasn't sure. If I baby it down the interstate, I get about 300 miles to a tank, maybe 330, but 18's plus low-pro tires make my speedo read a little high, and I would think it should be getting way more miles than that anyway. I assume it should be about 500 miles if it's getting around 29 mpg on straight up long distance interstate driving (which I do often).

Also, I deleted my knock sensor with a 1 megaohm .5 watt resistor since the knock sensor was bad. The SR has never quite seemed as fast as I thought it should be (stock t25g, FMIC, exhaust, roughly 9psi), but I'm really not sure. I assume that an improper knock sensor signal will pull timing and cause it to feel weaker, but when I compare the datalogs of my timing to the datalogs of my friend Scott's datalogs (same mods, redtop SR), they look almost identical.
My knock sensor is "deleted" and doesn't throw any codes, and his knock sensor is bad/unplugged and actually throws the code immediately and every time. Perhaps I used the wrong resistor? Maybe .5 watt isn't correct? Maybe the signal is wrong enough to make the engine pull timing as if it was detecting knock, but not too wrong to the point where it throws the knock sensor error code? When I deleted the knock sensor, I wired the 1M ohm . resistor in by snipping the knock sensor wire about 6 inches from the computer, then putting in the resistor then putting the other end to ground right there near the ECU mount.

Here's some screenshots of the datalog results.
me = Casey, my friend = Scott (just to prevent any confusion lol)








I appreciate any help/insight you guys have to offer!

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omgosh

What are you trying to figure out? Your knock sensor is not working, and neither is the o2, so fix it? lol

The o2 data displayed by your friends log doesnt appear to be right either. During a pull you should see .8 - .9 volts at least depending on how rich your tune is. None of this matters anyway though because you should be tuning with a wideband.

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cbh148

It's not so much what I'm trying to figure out, but rather seeking advice on what it appears like my problem is and advice on how to correct it. I figured I'd give myself the best chance by providing useful details and whatnot because I didn't want to drop another poorly composed, vaguely outlined "wtfhelp" thread. I've hardly ever had to mess with the electronics on these cars, and this is my first SR (had KAT, CA18, etc) so most all of this is kinda uncharted territory for me, so I'm not too familiar with it all yet.
I'd like to know:
A) why my o2 sensor isn't working,
B) what the o2 readings should look like (thought I heard that skinny o2 sensors act different than the normal, more common fatty o2 sensors),
C) if my knock sensor is actually deleted/bypassed like I intend for it to be, and if not, then what should be done to remedy it
I don't have a knock sensor. I attempted to delete it with a 1M ohm, .5 watt resistor placed on the knock sensor wire that I cut just a couple of inches from the ECU then grounded to the chassis near the ECU mounting holes.
Ok that's good to hear. As mentioned earlier in this post, I wasn't sure if the skinny o2 was supposed to cycle up and down like typical narrowbands do. And both my car and my friend's car are on stock tune/turbo/cams/everything except FMIC, exhaust, and intake.
I'm not tuning anything. I'm just aiming to get my SR in good shape to get the mpg's that it's supposed to yield (o2 sensor) as well as having it actually produce the power it's supposed to make (knock sensor).
Thanks for the reply! Keep em coming people lol

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omgosh

Ah, you're right about the sensors reading differently. I forgot the skinny sensor does indeed show less voltage than the usdm one. So yeah, Id say the o2 readings actually do make sense on the second log. My bad. You will be able to observe the o2 cycling at idle during closed loop. During wide open you will still get a reading but its not really useful for comparing to anything other than itself.

As for your timing curve; Can you not monitor knock? It looks like a stock timing curve to me. Id say the knock sensor trick worked. Could be a little smoother but not bad. It looks alot better than your friends log. The timing is supposed to drop to about 8-10* during peak torque then steadily climb to ~20* by redline.. If you look at your log from 5000-6000 rpms the timing goes from 14* to 19*. Your friends only goes from 10* to 14* during the 5-6k segment. Also his TPS is not right. lol

You really should get the knock sensor working though. Its there for a reason IMO.

And for the o2, just bust out the multimeter and start probing wires. GL

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cbh148

Ok so if I'm right about skinny o2 sensor readings appearing different than fatty o2's, what should skinny o2 readings look like?
Unless I'm missing something, I don't think so
I was expecting to be able to see the knock readings but I haven't seen anything about it. Perhaps ECUtalk and OBD Scantech just can't do this?
I was under the impression that they're pretty much useless in saving the engine since they're late to react and/or false a lot of the time. And I believe I heard that, even when they're in perfect operating condition, they still falsely pick up on knock and slightly retard timing because of it. This could all very well be wrong though, I have no idea.
Ok so it should be pretty simple right? Just like 12v power, signal, ground? I'm excited to get that sorted out and start getting some respectable mpg's! Once again, I'm thankful for the help!

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redcolorlook

that right,You really should get the knock sensor working though. Its there for a reason IMO. thanks

cbh148

I mean I'm sure Nissan meant well by having a predetonation sensor on the engine, but I'm sure they also meant well when they included plastic timing chain guides on the KA that always get chewed up and cause sounds/issues.

And I've always heard that having stiffer engine mounts and/or an engine torque damper and/or lots of other aftermarket goodies can also cause the knock sensor to trip up even more and falsely detect knock (and needlessly retard timing because of it). Not to mention, seems like every single person who has deleted their knock sensor had nothing but good things to say about it with no catastrophic regret stories that I'm aware of.

Anybody else care to chime in about if my timing curve looks appropriate? Is my .5 watt 1M ohm resistor ok? Or should I have gotten the 1 watt version of that resistor? No idea if that makes any difference.

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cbh148

So after getting to investigate a little further last night, it looks like my redtop's skinny o2 sensor plug has good continuity on the signal wire (white wire on harness side of plug, black wire on sensor side) between the ECU pin 19 and the o2 sensor plug.
It also has good continuity on the ground wire (black wire on harness side of plug, white wire on sensor side) between the chassis and the o2 sensor plug.

However, on the power wire (brown wire on harness side of plug, red wire on sensor side), it wouldn't read any voltage at all with the key turned on. I'm assuming it's supposed to get 12V.

So I cut the brown wire and ran an extension to the fuse box and put it on the fuel pump fuse (right side) just to test how it would act with 12V switched power. Well when I turned the key on, the o2 sensor began getting warm which I bet it wasn't doing before.

I got my Consult cable out to see if ECUtalk would now show something other than 0 voltage for my o2 sensor, but for some reason it suddenly wouldn't connect to my car. OBD Scantech couldn't connect either ("Initial Error"). Tried my friend's laptop and it was the same. Dunno what happened.

Checked for continuity between the dash Consult plug and the ECU plug, and all 3 green wires checked fine (green, green/white, green/black) along with the ground wire.

Maybe my ebay Consult USB cable crapped out on me after about a month of light use? Gonna try to find another 90's Nissan to connect to to see if I can pinpoint whether it's my car or my cable that's suddenly the issue.

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cbh148

***Update*** Tried the Consult cable on my bone stock vert and it connected immediately with no issues, so whatever it is that's causing both ECUtalk and OBD Scantech to not connect to my SR hatch must be specific to that car in particular. Not sure if it's the dash harness suddenly going bad or if I somehow screwed my ECU by running 12v straight from the fuel pump fuse to the o2 sensor power wire (which I assumed was basically how it's supposed to be? 12v switched power to the o2). Gonna try a spare ECU tomorrow to see if it's any different. I'll do it with no o2 sensor power at first, and if Consult connects then I'll add the o2 power back again to see if that makes it quit again. Also, in light of my Consult setup being MIA on my SR car, I had my mate hold the multimeter contacts on the o2 sensor signal wire (right at the ECU) and ground while we went to class this evening. It showed voltage jumping around after the first minute or two of driving, so I assume that's a good sign that my o2 sensor might now be functioning since I temporarily ghetto rigged a power wire to the o2 sensor. Seemed like my throttle response was different when I first started driving it with what I assume is a properly working o2 sensor (on this SR that I've been driving for a year now with no power ever going to the o2 sensor until now). Does this sound about right?

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