I just swapped a Y8 into my DX hatch and currently don't have the secondary O2 sensor hooked up. My DX had both sensors on the main engine harness, while the EX has one sensor on the engine harness and one that connects to the dash harness. I used the EX engine harness and want to know if my DX dash harness has a plug for the secondary O2 sensor. My only other option would be to run extend the wires for the sensor and pin it directly into the ECU plug. Please help. Thanks.

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Anyone? Bump...

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I did the same swap in a ek hatch.I used the ex harness.The secondary o2 on a ex model is ran through the dash harness.If you get wiring pinouts from a ex,you will see that the wires come from the green plug from the dash harnness and routes from the plug that goes thought the floor on a ex model to the secondary o2.I just made a little sub harness and ran it from the access hole on the tunnel to the wire pinouts in the green plug.I will see if I have the notes I made on it and post it up.

 

Wait, so you used an EX dash harness? Or is there a plug for the secondary O2 sensor on the engine harness? Please elaborate. Thanks.

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No I used the dx dash harness.If you can source a ex dash harness,you could swap it and the plug would be there for you to plug the secondary o2.Iwill try to explain this a little better.On the ex motor harness,there is a green plug that plugs into a plug inside by the ecu.That green plug on a ex dash harness is where the secondary o2 is routed to.Since the dx harness has both o2's wired in front on the motor,they are wired directly to the ecu plugs.But on a ex model the secondary o2 is in the back of the cat,and runs up through the floor to a short sub harness that routes though the dash harness to that grren plug by the ecu.From that green plug on a ex,it routes the wires back out to the engine harness and then back into the ecu.I just found the pin outs for the secondary o2(for a ex ecu) and just made a sub harness that goes from under the floor (if you take your console out you will see a rubber plug in the floor,you can route the o2 wiring through there just like on a ex model)then run the four wires into the wires that are already in place on the green plug on your ex harness.Or another alternative is use you dx harness and extend the wires to reach the secondary o2.Then take you vtec and oil pressure switch wires from the ex harness and run them straight to the ecu by making a sub harness for that.That might be easier than wiring the o2.I will get more info from my friend who helped my wire up the o2.Sorry if I am confusing you.It's one of those things that if I could show you on the car you would under- stand it better.I will see if a can make a mock-up and post pics if you don't figure it out.

 

I *think* I understand. Can I just extend the wires from the O2 sensor to plug into the green plug that you were talking about? Or if the plugs are different, I just need to make a conversion harness to adapt the O2's plug to the green plug?

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the green plugs are the same soyou can add them to it.Instead of saying:"dash" harness,I should be saying "inside on the firewall behind the dask harness".That is really where the green plug comes from.just run the wires to the correct wire locations where they a are normaly located on a ex.You will figure it out i'm sure.

 

Now that i'm looking at it, I understand what you're saying. I got a pinout diagram for the wiring harnesses, but i'm still confused a couple issues. 1) The O2 sensor is a four-wire version, the white/red goes to the ecu as the signal, but i'm not sure about the others. I went to the Honda dealership and got the EX O2 subharness and it changes the green wire on the sensor to a green/white wire, which I can't find at the ECU junction. Should that be changed again to the green/black wire on the engine harness? And did you just run off the two black wires and ground them somewhere, or should they be integrated into the harness as well? Thanks again.

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