I am going to be extending my secondary O2 sensor harness so that I can place my O2 sensors behind the main cat. (I've installed headers and will be installing the Cattman Fast Cat and Cat back)

Is it possible to wire up 1 O2 Sensor in such a way that the car thinks there are two? I know I could bypass the heater circuit on the second sensor with a 20 Ohm resistor but can the signal be duplicated to fool the ECU? How would I do this?

 

Sorry bro the only way yoy can do that is with a dual sim

 

There is a site that sells the extension harness just search for post from me wirh the keyword o2 sensors

 

Don't do that.

 

Why not? Isn't that the purpose of the secondary O2's to monitor the condition of the catalytic converter?

 

Pretty sure because before the car is warm the primary sensors are wanting the reading after the precats. The main cat does not work well until it warms up. If you have installed headers you don't have pre-cats so if you are reading exhaust gas after the main cat you will probably get an ses light.

 

Wires will be longer than advised.
Oxygen readings will be out of the normal specification
Nissan uses secondary sensors add back ups. They actually do contribute some control over the engine, especially if the reading from a primary sensor seems odd.

As for wiring 2 sensors into 1, I can't immediately think if a reason it won't work if you use a resistor for the heater. But I don't really know.

The question is why? Why would you ever bother?

 

Yup. And O2 sensor signal wire is finicky and prone to mishaps/bad readings when cut/soldered/extended. And that would be a fairly long extension.

My primaries are plugged into the primary bung/port (mechanical, not electronic) and I have no secondary codes, as in, apparently they(secondaries) don't seem to mind the no cat having exhaust stream.

Also, 03BLKTE, (IIRC) has had his headers and IIRC, secondaries just hanging out in the engine bay, or maybe they;re bunged, but he has no codes, hasn't for years.

 

Well thanks for the heads up. I was really trying to do things the right way. I guess I could just plug them in and see what happens. Will still need a new bung added. I plugged the primary bung on the rear header (OBX) and used the secondary bung for my rear primary. I'll add the one in and see if the code goes away and if it does I'll have a new bung welded in for the second one.

 

Let us know how that goes. I have been trying to do this for years. I, obviously do have primary codes since they are totally non-existent.

 

I was under the impression that the car wouldn't run properly without primaries. I don't have any codes for the primary o2 Sensors though I did have to extend the rear harness a bit (the harness cable is just plain copper, I wouldn't try extending the sensor wire). I may throw that front secondary on there tomorrow. Shouldn't take but a few minutes if the cable reaches. I'm expecting my Cattman Cat and Catback tomorrow as well but won't be able to get to that until next weekend (I have my daughter this weekend and won't be spending that time under the car).

 

if you're primaries are disconnected the secondaries have no reference and therefore aren't known to be wrong. Code thrown for primaries because they are the known issue. If they were installed you would likely have a secondary code appear. Unless I'm missing something. Why DO you have it set up that way anyhow

 

Primaries not long enough to reach header ports, so secondaries are plugged in their place, since they're longer.

I know of at least 2 people who either have their)2's hanging in the engine bay or bunged into the headers where they reach and no codes. Whenever time permits I'm going to do it opposite, plug primaries and secondaries but not have the secondaries in the loop, and if needed, add a couple of bungs for the secondaries.

 

Ahhh I see.