ECU's & Harnesses Differs With 02 Sensor Wiring!!!!! & Running Rich Explained!! - SR20 Forum
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post #1 of 61 (permalink) Old 07-29-2005, 07:21 PM Thread Starter
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ECU's & Harnesses Differs With 02 Sensor Wiring!!!!! & Running Rich Explained!!

I have Definately Secured this Statement with several cars. I have been wondering why my car was running so rich and I managed to take apart and strip my whole harness to neaten up things a little bit and discovered this verry useful knowledge. :naughty

NOTE: Late model Blacktops (TYPE-X) use a different harness Layout then the two mentioned below. If you need a pinout for that harness please email me or post below.


ok here it goes:

Early Blacktop Harness' use a Brown/Yellow Stripe (pin 114) wire to give the Heated Oxygen Sensor a Ground/Internal Standpoint.

So the E5/E6 Ecu's (Early Blacktop Computer) is needed if you are using an Early Blacktop Harness!! Otherwise the Heated Oxygen Sensor will not complete the circuit and give a legitimate signal to the ECU (via pin 19)

Early Model Redtop Harness' use a black wire that is looped up by the Injectors and Iacv in the harness and shares a ground with them by a crimped union of ground wires that bolt to the Intake Manifold itself

So the E62/E63 Ecu's (Early Redtop Computer) is needed if you dont see any Brown/Yellow Stripe wire in your harness on pin 114 of the ECU Plug.

But you could use an E5/E6 Computer with a Redtop harness, because the harness is self-grounding.

So the verdict is that your Heated Oxygen Sensor WONT work if you have a Early Model Blacktop Harness and a E62/63 ECU. Because it doesnt have a ground to complete the circuit and send signal to the ecu.

The Heated Oxygen Sensor Plug comming from the harness if you put it facing you with the Hump (clip) on the top goes from left to right like this:

|Ground|..............|Signal Out|............|Power|
^ ............................^..................... ...^
(b/y or Blk) (White) (Differs)


You can test to see if your getting signal by letting the car warm up at idle and pop the hood. With the 02 Sensor Plugged in still, take your multimeter and set it in Volts DC and stick your red probe/lead in the middle wire through the back of the plug, you should be seeing somewhere between .3 to .9 (+/- a little bit) but no higher than 1 or no lower then 0.

When you rev the engine a little bit the voltage should bounce around more frequently (cycling voltage) within the specs I told you, this means its reading properly.

This will tell you if your 02 Sensor is sending proper signal out through the Middle (Thick White) wire. If its sending too HIGH, then you have an incompatible 02 sensor or its faulty. If you have none then you have your wires wrong...or possible faulty 02 sensor.

You can quickly test continuity in the 02 sensor itself by unplugging the sensor and probing the two outter prongs and by having your multimeter read in Ohms, you should see anywhere from 3-1,000 Ohms according to FSM.

I hope someone can give me some feedback if you read this. I am almost 100% sure about this because I have tested and tried this.

ALSO WHY WE RUN RICH?

Most of us have the 190 or 255 LPH walboro and it bumps up the fuel pressure at idle.... which is supposed to be 36 at idle with hose connected to the FPR......and if you unplug it it should read 44 accordingly to the FSM...

If you have a Fuel Pressure Gauge and notice it sits high (40 ish) at idle, you can also tag this on to the list of reasons why we run a little rich.

This can be avoided by re-setting your base fuel pressure with a Adjustable Fuel Pressure Regulator that can be purchased by any of our sponsors here at NICO or anywhere on the web (ebay,others)


Also the Scale for an oxygen sensor is :

closer to .0 is LEAN

closer to .9 is RICH
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post #2 of 61 (permalink) Old 07-29-2005, 07:31 PM
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wow. all i got to say is that should be a sticky

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post #3 of 61 (permalink) Old 07-29-2005, 07:32 PM Thread Starter
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Thank you
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post #4 of 61 (permalink) Old 07-30-2005, 04:33 AM Thread Starter
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ALSO:

If our 02 sensor works, the higher fuel pressure is usually not a problem due to ECU correction taking place. So basically if we run rich due to no 02.....not only does the computer not know our possible AFR's, but it automatically compensates by running a richer map for safeguarding the engine's running cycle, and you can tack on the extra fuel pressure to that one . So if we run rich....we run REALLY RICH

Any Feedback?
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post #5 of 61 (permalink) Old 07-30-2005, 12:50 PM
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All in all, you have to use the correct O2 sensor for the ECU you are running, there are two different types of o2 sesnors car manufactures use, do a search I posted info on this if wanna find out (TITANIA VS ZIRCONIA 02 SENORS) AKA Fat and Skinny, by the way TITANIA sensors are mainly used on high end cars as they are more expansive and faster responding.
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post #6 of 61 (permalink) Old 07-30-2005, 12:52 PM
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But they are not interchangable IIRC TITANIA works off of wide range of varible resistance and ZIRCONIA works off of a scale of 0-1 volt an dthe ECU is therefore programed accordingly to reach a specific o2 sensor.
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post #7 of 61 (permalink) Old 07-30-2005, 12:57 PM
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A simple test to see what ECU you have is with the ignition on but car not started prob the o2 sesnor signal wire and you should get .32volts for a ZIRCONIA programed ECU, this is my knowledge from many USDM B13 and B14 equiped with ZIRCONIA AKA Fat o2 sesnors.

TITANIA equiped ECU would produce nothing at all or something very different I for got what I got on the only TITANIA ECU I came accross.
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post #8 of 61 (permalink) Old 07-30-2005, 04:28 PM Thread Starter
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Verry right. I have discovered on my friends redtop that he was running the skinny type that was putting out 1.3 volts to the ecu and making it go bonkers. So we took out the 02 sensor bung and tapped a 18mm x 1.5 thread and fit a nice FAT type 02 sensor in and he is running mint.

Thanks for the additional info.
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post #9 of 61 (permalink) Old 08-29-2005, 12:16 PM
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You guys have no idea how much I needed to hear this!
I get like 10mpg on my redtop, and i have a Walbro pump.
I replaced the O2 sensor, FPR, MAF, Plugs, Coil Packs, and ready to do the ECU.
But here's my problem:
The guy who owned the car before me, used the factory Vert harness and kept the single wire O2. I don't know what pins are used on the redtop ECU to run the Power and ground for the 3 wire. Also, I have a dump pipe with a small O2 bung and the large one on the car.
So, I checked my stock ecu and the O2 wire was reading .20v.
Do you guys know what O2 sensor the stock redtops used?
Thanks,
Jason

Last edited by Zadok; 08-29-2005 at 12:42 PM.
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post #10 of 61 (permalink) Old 08-29-2005, 02:04 PM
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Again concern yourself with what ECU you are using, so you should also be 100% that you do in fact have a redtop ecu and use the correct o2 sensor for that ECU, I know sometimes ECU are mismatched.
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post #11 of 61 (permalink) Old 08-29-2005, 04:42 PM
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I went from a skinny O2 to a fat O2 on my redtop with redtop 62 ECU and had NO difference in performance or driveability whatsoever. I get over 30 mpg on the highway.

There's another guy here in town running a skinny (redtop) O2 with blacktop E5 ECU, and his car runs just as well. I'm not saying the above info is wrong but I think there's some more digging to be done.

FWIW, there's a long thread on Zilvia somewhere that essentially states that all narrow-band O2 sensors are created equal and you might as well just get one that fits the bung and will wire in correctly.

My $.02

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post #12 of 61 (permalink) Old 08-29-2005, 04:52 PM
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No there is a night and day difference bewteen the two oxygen sensors TITANIA vs ZIRCONIA they report back to the ECU tottally different.

Anyone thats wants to read more about it here do a search with my name with TITANIA vs ZIRCONIA and you should find quite a bit of info on the subject.
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post #13 of 61 (permalink) Old 08-29-2005, 04:55 PM
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The E5 SR20DET ECU uses a skinny (TITANIA) o2 senor thats why it works well and im sure some redtop use teh skinny also just as some bluebirds did to..

Nissan put the better o2 sensors (TITANIA) in the RNN14 Pulsar GTi-R and the U12 Bluebird.
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post #14 of 61 (permalink) Old 08-29-2005, 05:26 PM
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charlie as always your information is appreciated, thank you.

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post #15 of 61 (permalink) Old 08-29-2005, 05:31 PM Thread Starter
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guess my information isnt appreciated around here huh....
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post #16 of 61 (permalink) Old 08-29-2005, 09:54 PM
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How ofter are a\f gauges wrong?
I have an auto meter, and its always seemed to work good. The problem is, my a\f is showing normal, but I can seem the fuel coming out the exhaust, and watch the gas drop.
I guess I should include that I have a 2.5" downpipe and exhaust with no cat. and a T28.

Last edited by Zadok; 08-29-2005 at 09:56 PM.
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post #17 of 61 (permalink) Old 08-29-2005, 11:21 PM Thread Starter
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well that may be condensation too.......if thats gas..you have a major issue and you should be running all crappy at idle......probably a lower injector o-ring or a worn leaky injector solenoid......or a stuck FPR or a mess up o2 sensor....or the wiring...or a dirty mafs....or miswired/misgrounded mafs......or something of that nature........or too retarted of a base timing......**** keep going??? misfiring coilpack.....

im not haggling just really tired.....check all of that though....


oh yea and TPS way off.....or bad coolant temp sensor for the ECU.......or just plain bad ecu.....or maybe its just condensation....who knows....maybe a fuel leak....dripping onto the muffler...making it look like its comming from inside???
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post #18 of 61 (permalink) Old 09-06-2005, 10:11 PM
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ok, I meant the gas gauge drop.
And I meant unburnt fuel comes out the exhaust.
anyways, i'm buying a nismo fpr and going to adust the fuel to the factory settings.
But what I really need is a wiring diagram on how the wire up a 3 wire O2 sensor on a retop.
Again, I have a converted KA harness with the original single wire setup, so I need to know where to put the power and ground wires for the heated O2 sensor.
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post #19 of 61 (permalink) Old 09-07-2005, 12:06 AM Thread Starter
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im pretty sure that the middle wire is signal....and the two outside are positive and ground.....not sure which is wich.....

i have a feeling that if your looking at the 3 wire 02 so that the plug is facing you and the wires are going away from you from the plug....the right hand one is ground.....and the left one is signal.......remember that the brown wire (dunno if u have one since u got the KA harness..) is power...........so if i were you just put a ground to that wire all the way to the right.....signal goes in middle......and that goes to pin 19 on your ecu......and give the one on the left power from the fuel pump relay.......
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post #20 of 61 (permalink) Old 09-09-2005, 11:55 AM
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Thanks for the info!
So the power comes from the fuel pump relay and the ground, is just that, a ground.
Hrmmm!
I think I can swing that.
Thanks.

Last edited by Zadok; 09-09-2005 at 12:02 PM.
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