OBDII passing emissions question. Bad cat. Splicing 3 wire to 4 wire oxygen sensor?

[az_240]

Ive been trying to get my OBDII 1997 240sx to pass emissions unsuccesfully. It throws a bad cat code so I purchased a working OBDII cat from a 1996 240.

Problem is the o2 sensors are different. The 97 o2 sensor is a 4 wire and the 96 o2 sensor is a 3 wire.

I was wondering if I can somehow get the 3 wire o2 sensor to work on my 4 wire harness and pass?

Colors on the 3 wire are red, black, and white. Colors on the 4 wire are black, grey and 2 whites.

Any help is appreciated.

Thanks

[omgRWDgoodness!]

I don't think the problem is your catalytic converter, because the O2 sensor doesn't plug in to it. I'm not sure about the zenki, but on the kouki the O2 sensor goes into the downpipe, so maybe you should take a look at that? You might have a leak or something..

[projectRDM]

The converter is part of the downpipe.

To answer your question though, no. You'll need to weld the right size bung and use the 4wire sensor. The ECU is different and the EVAP setup is slightly different, as is the harness. There's no way to just rewire the correct sensor.

[omgRWDgoodness!]

The converter is part of the downpipe.

***t, I thought he was referring to the 2nd catalytic converter :duh:

[az_240]

I do not have a leak.


Shit!!! So that downpipe I bought is worthless to me! My only option is to somehow get a working 97-98 downpipe/o2...

This is not going to be easy

[Rabboni]

Dont mess with rewiring any emissions device. If a smog tech sees any cut or splices wires it becomes an automatic fail for tampering with emissions devices. So, dont rewire, but if you do make sure the tech cant see it.

[az_240]

uh just figured out I cannot splice any wires anyway....

[projectRDM]

I do not have a leak.


Shit!!! So that downpipe I bought is worthless to me! My only option is to somehow get a working 97-98 downpipe/o2...

This is not going to be easy

No, read what I said.

Plug the existing O2 hole. Drill another hole, weld the correct size bung to the downpipe. Screw the correct O2 sensor in. Done. The downpipe is identical besides the O2 fitting.

[az_240]

I learned ka-t guys go with the 96 downpipe/o2 and ECU to help with tuning... I think I'm just going to get a 96 ecu and go that route since I already have the downpipe.

A new o2 sensor is $70 and I'd rather not go through the work to try and make it fit.

Thanks for the help

[projectRDM]

Legally you can't do that.

In a 1997-1998 model you would need to swap in a 1996 ECU, harness, and matching sensors (that differ). Plus there are changes to the A/C control system that will need to repinned in the harness.

Way damn easier to just install the correct sensor.

[az_240]

^oh I did not know that... the guy on my local forum made it sound like it was no big deal.

You truely are a zilvia god.

I guess I will just try to fab up that downpipe and get a new o2.

Thanks