Catalytic converters and P420 P430

[Hetfield03]

Was just wondering if my MRT axle back is the culprit for my cats going bad, or is it an independent problem that just happens?

I'm told since the codes are on the downside, out will only throw codes but nothing will happen, but at the same time, when sitting at stop lights, I hate seeing the rpms fluctuating slightly.

Will the Mini Cat O2 Sensor CEL FIX from Bigdaddies eliminate the codes and problem, or will I need new cats too? And if so, what cats for a v6?

Thanks in advance.

[KillboyPowerhead]

An axle-back should have no influence on the cats/those codes.

Here is something I posted on HPTuners regarding the P0420 I got after installing Mace cams:

Tuning an LFX (3.6 V6 DOHC) but posting this here since it'll get more views.

Awhile back I installed Mace cams and within a few weeks got the P0420 code (hadn't done any tuning at this point and was still running a tune from my previous tuner). Figured it was due to running rich (was 10 - 15% rich across the VVE table when I first started tuning), but now that the fueling is within 2% everywhere, the factory O2 sensor is back in and I haven't been downloading a tune every day (engine light/codes reset), the code eventually came back. Believe the post cat sensors are indicating that the cats are functioning properly as they show a mostly constant voltage, but the voltage is a bit high. While driving at steady state, bank 1 is averaging about 765 - 770 mV while bank 2 is averaging 690 - 695 mV. I'm not getting a P0430 code (bank 2) so I wonder if the code triggers when the average voltage is over 700 or 750 mV. Unfortunately I didn't do much logging before the cams so not sure what the voltage "should" be. I also have high-flow cats from Solo but have been running these for a few years with no codes.

Noticed in one log that when the intake cams advanced (went from cruising to ~50% throttle) the post cat voltages dropped, so I added 4 degrees to both intake and exhaust in the cruising areas (extra 8 degrees overlap) and the voltages for both banks started averaging under 700 mV during the same cruising speed as before.

Anyone know if adding extra overlap is a solution to the P0420 code? Is the higher voltage indicating that I should be adding more overlap? Or is a higher voltage just a result of the high-flow cats and cams (and/or VVT tuning), and there isn't necessarily anything wrong with having a higher voltage? I'm guessing the voltages raised a bit compared to factory after installing the cats but as mentioned I didn't do any scanning. I know I can just turn off the MIL/set to No Error Reported, but not sure if this would still prevent me from remote starting (code hasn't come back since I reset it yesterday so I can't confirm yet, but guess I'll find out in a few days). In any case it would be nice to get rid of the code without just disabling it.

FYI a higher voltage means a richer mixture.

Not sure what CEL FIX you're referring too, but I've read that adding an extender to the O2 sensor can "fix" the issue because it'll move the sensor further away from the exhaust.

Also see this thread: https://www.camaro5.com/forums/showthread.php?t=619467

[Hetfield03]

Yeah, the cel fix from a place like Bigdaddies or one can be made yourself. Yup, those O2 sensor extenders.
I'm gonna probably go that route.