Long story short, I have a 2001 s2000 as well as a 2000 ITR.

The ITR was formerly a track car, and has a T1R response header as well as a T1R cat with NO o2 bung and T1R exhaust.

The ITR has no o2 sensors hooked up due to the primary being a PLX M250 wideband, and the T1R cat not having a bung for an o2 sensor.

Since I have the T1R track pipe on the s2000 also WITH a bung for the o2 sensor, I was going to plug the wideband sensor into that and that will eliminate that o2 sensor. I was then planning on taking the SECONDARY o2 sensor off of my s2000, and putting it in place of the PRIMARY o2 sensor on the ITR.

Would my SECONDARY o2 sensor of the s2000, fit the PRIMARY o2 sensor on the ITR - as in harness for harness?

 

I'm thinking no. Even if the harness fits, secondary O2 sensors are usually different than the primary one, and not as sensitive as the primary. I think it's there more to just compare emissions readings with the primary to confirm the presence of the catalytic converter. It doesn't really have any effect on the ECU's adjustment of A/F ratio like the primary one does.