mine has an O2 sensor that was hooked in behind the cat and mine is a california version so it did have an O2 sensor in 75 cuz thats when the laws started the rest of the country they didnt have them til the zx's i believe

Well, mine is a 78 California car and it has no oxygen sensor. Nor was I able to find one on the microfiche or in the FSM.

1977 OEM 280z: thirty some years one owner.

No oxygen sensor on mine.

And thats a fact jack

mine has an O2 sensor that was hooked in behind the cat and mine is a california version so it did have an O2 sensor in 75 cuz thats when the laws started the rest of the country they didnt have them til the zx's i believe

The thread is three years old. The kid that posted the question had some kind of hack job oxygen sensor that was installed in the exhaust pipe behind the catalitic converter for whatever reason. And he possesed some misinformation. Nissan definately never put them there on any S30 or S130. On the S130, it was in the exhaust manifold. Nissan actually called it an 'exhaust gas sensor'. There is no provision in the pre-79 ECU to operate one. He had all kinds of other problems with the car and I'm not sure he ever worked them out since he hasn't posted here in over two years. But you're right. No sensor on a 280Z no matter what year or state.