O2 Sensor difference
 

I recently purchased an O2 sensor for my 92 Maxima and noticed it had a second connector (one blue wire). It has also the 3 wire connector (same as what's already in there). Research shows that it is a design that was for the 89 Maxima. 90.5+ used the one that has one connector. What's the second connector for?

More importantly, can I use this O2 sensor for my updated design?

you can use it without worry.
just check the wire length.

we thought mine was bad so my friend had from a gxe that was a spare and I have a vg se so it should be interchangeable, but the one he had has only one plug while the one I bought from you internetautomar had two plugs. The one I got from you obviously fit, but we were curious why the one he had had only one plug

What is the 2nd plug with the blue wire coming out of it for?

...tHat must be the relay -reset wire...

dunno, I know that the 2nd connector is just tapped into one of the other 3 wires.
so it's not a true 4 wire 2

...I thought the blue was the nos consumptin lead?