I found on this forum that one of the members had put a resistor/capacitor smoothing circuit into the post-cat signal lines ("search" is a wonderful thing!). I didn't find any follow-up; who has done this, and was it a long-term fix?

I'm having problems with my post-cat sensor tracking the pre-cat too closely, despite a new cat and two new sensors. I live in a place where they do a periodic inspection, but rely on the OBD II rather than a tailpipe sniff, which I would probably pass. So, I get a CEL because the post-cat jumps around too much. This approach -- simply smoothing the signal -- seems like a good solution, hence the question.

Apologies if this has been answered already.

 

You can build an o2 simulator that will take care of the whole thing for you.