primary 02 sensor and secondary o2 sensor in b16a?

[VTec1987]

Is the such thing as secondary 02 sensor? If so where is it located?
I know the primary o2 sensor is on the end of the headers.

[omgzilla]

The secondary O2 sensor should be after the catalytic converter.

I haven't looked myself, but it seems logical to be positioned after the cat.

Also appears so according to the workshop manual. I think it might depend on the 'OBD' spec though.

Any particular reason?

[Limbo]

the primary one is on the front of the header and the secondary one is on the end of the header. THis is only for a b16a1. B16a2 only has one O2 sensor at end of header

[omgzilla]

That's strange. The workshop manual shows otherwise Limbo:
http://img249.imageshack.us/img249/3174/wsmo2uu2.jpg

Hmmmm, you're probably right.

I should probably go and have a look at mine. Hahah

[Limbo]

I see why now you have 2.
The second one is a cat sensor. Oz spec ones don't have that one.

You don't need the cat sensor one. Most imports i've seen cut it off. It only registered if the cat gets too hot.

[omgzilla]

I thought the 2nd O2 sensor was to tell if the cat converter was operating properly.

For example: Taking a reading of the exhaust gas before the cat (via Primary O2 Sensor) and then seeing how well the cat was doing it's job by comparing with the secondary O2 Sensor reading?

Or is this only on later model cars with more strict emissions laws?