What is the purpose of the secondary O2 sensors on a VE SS?

[Xjas]

I just climbed under my car (VE SSV) and noticed the I have an exhaust leak at the rear of one cat before the secondary (rear most) O2 sensor.
I would assume this leak will affect the reading on that sensor but will the ECU adjust fueling to compesate or is that O2 sensor only used to verify cat operation?
I am going away tonight on a trip and dont have time to fix it before I go away, just wondering if I should turn of the LTFTs in the ECU so the ECU doesnt try to correct for this incorrect o2 reading.

[Dieselman]

They only check to see if your cats are working. Will throw a code if it thinks the cats are cactus

[Xjas]

Thanks, thats what I thought but wasn't sure, I haven't had it throw any codes yet, the leaks not that bad but I thought if the rear O2s contribute to the fuel trims then air getting in would cause the ECU to think its lean and dump fuel in to compensate, not good for fuel economy on a 2000km trip.

[surfwagon]

As said above just to check the cats are working but they will usually throw a code if the cats are replaced with cats that flow better (don't convert the noxious gases as well).



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[Xjas]

As said above just to check the cats are working but they will usually throw a code if the cats are replaced with cats that flow better (don't convert the noxious gases as well).

Thanks, I can deal with fault codes, I have HP tuners and am slowerly learning to tune myself, just had to be sure the O2s reading off wouldn't screw up my fueling in closed loop.