ECM 4801 + ECM 130A - What am I missing?

[cantabrian]

Hi, all,

I have a recurring code that I need help fixing. I have a 2004 xc70, with about 175K on it. Here's the story on my codes (catalytic, and air leakage):

- I have ECM 4801 coming up (Three-way catalytic converter efficiency, bank 1 - Faulty signal). It's turning the check engine light on. It sometimes stay off for a couple days (then back on once driven enough). From what I've read in VIDA and on forums, this can be many things. Which is my problem. The thing to know about my particular situation is that I (probably stupidly) had a local muffler guy install a cheap aftermarket cat about a month ago. He just welded it in. The problem was that the old one was cracked, and I didn't think it could be welded shut properly. So after reading some forum posts about this, I decided it was probably ok. I figured if it loses catalyst after a couple years, I could get another cheap one. So, maybe the code is just from that--the fact that Volvos like OEM parts. But from my reading of the VIDA values (see in these screenshots), it seems to be mostly in range. Could the code be coming up just because this cheap catalytic doesn't really operate well until it's fully warmed up? I still have the old one; I could see if I could get someone to weld it shut and weld it back on, though that seems a little crazy.

- Based on the above, I understand it could also be the O2 sensor. But, again, do the readings seem way off? I can provide more screenshots if you'd like. I've also replaced the MAF, btw.

- As for the ECM 130A (Air leakage intake), it's actually indicated yellow in VIDA (so, not a fully active fault, but something's there). My theory here is that it's the PCV system. Me and my mechanic both checked the vacuum hoses, and we didn't find a leak. To my knowledge, the PCV hasn't been replaced. So, it's due. But it passes the glove test, and there's no other real symptoms--except maybe this code? And could that be inspiring the ECM 4801 too?

- I just realized while reading around today that I didn't reset the fuel trims by disconnecting the battery and draining it after I got the new cat. So maybe I should try that?

In short: I'm wondering what steps to take, based on this history and these readings. What seems off? Is the PCV the first step I should take? Did I doom myself to 4801 codes with that cat decision? Any help appreciated.

Thanks.

[hoonk]

Did I doom myself to 4801 codes with that cat decision?

Maybe - some have used an o2 extender on the rear sensor to cure cat efficiency codes.

[cantabrian]

Thanks, hoonk. A spacer might be the trick. But I'd not want to delete the cat without knowing first that it was basically doing the job. Could someone with more knowledge and experience reading VIDA readouts let me know if mine look in range? I can offer more if the graphic display attached isn't enough to get a good sense of it. Here's one that shows what it looks like before it's really hot. Before the cat gets really hot, the numbers on the rear sense tend to be lower (like in the .20-.50 range). Might this be what's throwing the codes?