Thread: Front O2 sensor wiring

Of course the wires in the pic I drew are not correct, but that's the kind of shot I need to see.

ok, i dont have the plug on mine, because i went to a 4 way setup way back , but i can tell you this about the 3 wire setup.


Red and white are both for the heater circuit. Polarity does not matter. They occupy the "outside" wires on the plug (all but the middle wire) If that makes sense.

The middle wire (black) is the signal wire and goings to the ecu.

the only difference between the 3 wire and 4 wire setup is the signal ground wire on the 4 wire setup. on the 3 wire setup the signal ground is through the exhaust. Let me know if you need more help.



again the only important thing is that the signal (black) wire is in the middle the outer 2 are heater circuit wires, the polarity of which do not matter.

o wait, did u snip off both plugs? , if thats the case i saved the chassis side plug and i will have to take a look at it when i get home

Yep. Sure did. And the wires coming from the engine harness is what I can't figure out.

i snapped a few pics but didnt get to upload them, my wiring is all shrink wrapped but i got the plug, (from last nights memory) the plug has 3 wires (duh) the center wire is white and a bit thicker then the other 2 , and on the outside there is one that is red with a yellow stripe and the other i believe is orange. Outer wires dont matter as they are for the heater and the polarity doesnt matter, the inner white wire is the signal wire. Im going to search the fsm now to see if i can get more specifics on it.

I know I've seen the orange wires used for signal before, but that white/black wire being so heavily shielded, I thought that might be the signal.

take some pics of what you have, mine might have been shielded originally, if i saw it that heavily shielded , id prob assume that was a signal wire too

Look at F1 harness connector to correspond to your o2 sensor. Middle wire of o2 sensor is for signal.


3-2-1 at o2 sensor harness connector if you are looking at the sensor straight on.

THANK YOU!!!! I've been trying to find a diagram like that for a week and could not find it. Probably have overlooked it a thousand times...lol.

Okay. So for future refference, here is what I came up with:

For `96 200SX SE-R (possibly 95-97's?)

Brown /w yellow stripe ______________= +12v from ign fuse block
White or White /w black stripe _______= Front O2 sensor signal (ECU pin 46)
Orange wire ______________________= Front O2 sensor heater (ECU pin 115)

And here is the ECU pinout just in case someone needs it:



Thanks for all your help guys! Hopefully this will help anyone else that ever has this problem, or is just curious.

So, the CORRECT wiring for my '96 200SX SE-R (USDM), and maybe sentra's, IS:

[ECU]---Brown / Yellow ------[OEM 3 wire plug] ----- Red -----[Front O2 sensor]
[ECU]---White(Shielded) ------[OEM 3 wire plug] ----- White ---[Front O2 Sensor]
[ECU] --Orange ---------------[OEM 3 wire plug] -----Black ---[Front O2 sensor]

Hope this helps anyone else in the future.

P.S. My troubles were not a result of incorrect wiring, but a bad ignition switch/tumbler