Why does my o2 sensor have one wire

[alicbr]

I have a 1995 s14 with s13 red top sr and can’t figure out the o2 I need please help

[amc49]

Earlier ones if correct only need one wire the output, O2s make their own voltage. Later ones add a heater circuit to heat them faster to lower emissions.

[PapaSmurf2k3]

What's the problem?
Do you have a 1 wire O2 sensor and your harness is for a 4 wire?

[Hijacker]

Red top harnesses have heating elements in the O2 circuit, so it has an additional 2 wires. Only one wire is actually signaling to the ECU. It's been a while and I can't remember the wire colors off hand, but you only need to connect your single wire O2 sensor to the signal wire.