Lanos O2/lambda sensors

[Rodd1s]

The newer lanos' (ie: 2001 onwards) have two O2 sensors... what I want to know it does anyone know what the second sensor does or is used for? i know the engine runs without it, although a CEL is displayed.

i need to know whether i really need it as with the 4-2-1 manifold and new catalytic converter shifting everything down its not easy plumbing in another plug hole for the second sensor.

alternatively, would it be possible to emulate/fake the signal from the second o2 sensor? eg: applying a voltage/load to the 4-pin connecter?

edit: just realised where i posted this, its meant to be in engine/intake/exhaust area, not aftermarket... could admin move it please? thanks.

[gse_turbo]

the second O2 checks what the cat-con is doing and adjusts the fuel in turn. if the second O2 is reading too rich then the cat-con is not working correctly and the second O2 will have the computer lean out the motor until all emissions are burnt up by the cat-con.

don't remove it, you will have issues. I tried using a cell delete tube that pulls the second O2 out of the exhaust stream but that didn't seem to help. it would be nice to eliminate but without a stand-alone EMU I don't really know of a good way to go about it.

[Rodd1s]

so it does exactly as the first o2 sensor does, but is used like a secondary fuel trim input... thing.

anyone know what thread the o2 sensors use so i know which size nut to look out for?

[gse_turbo]

18x1.25, I believe

[Rodd1s]

18x1.25, I believe

cheers.

edit: sure it's not 18x1.5 ? because i cant find any lambda sensor adapters/bosses or even steel nuts with that thread.

[gse_turbo]

hhhmmm, maybe, I'll double check!

[Rodd1s]

well i got hold of a 18x1.5 adapter with the recess carved out to fit onto the exhaust pipe, so even if the thread dont fit, i'll make it fit.

[MMamdouh]

i was under the impression that the second O2 sensor is used to check the performance of the CAT... if it reads the same O2 level as the first sensor then the CAT is not working... basically this means you have to make the second sensor read less O2 than the first if you want to remove the CAT and avoid a CEL... this is doable by putting a spark plug seat on the second O2 sensor

MMamdouh

[Rodd1s]

confirmed, O2 sensor thread is 18x1.5