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.
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