I posted about this awhile back but haven't had time to try your suggestions until recently. So after installing new Bosch O2 sensors, after a couple of days, I started getting these 2 codes (P0430 & P0420) From a suggestion, I installed a non-fouler in S1 B1. Drove for a day, no codes, no pending codes and all O2 sensors were reading proper outputs .Next day started getting P0430 (not P0420) .after about a month of off and on driving P0P30 is now gone. All great news right???

My SEL comes on after 3 or 4 hours of driving after clearing codes. When I check codes, there are none. No current, no pending, no historic. I am still getting reading from all 4 O2 sensors. Why?

Side note, after installing the non-fouler, my gas milage went up a whole 2 MPG!!! The first time, I thought it was a fluke. The second, that I mis-calculated, but 3 times???

 

Why did you install a nonfowler on the front sensor? Don't do that. Your mileage went up because you're leaning out your engine. That's very bad.

 

Someone on here suggested I do that because I was getting p0430, p0420 and one other code right after installing all new 4 Bosch O2 sensors

 

The "correct" use of nonfowlers would be to put them on the rear sensors. It's still a band aid fix, though. You've got bad catalytic converters.

Definitely need to remove this from the front sensors before you cook your engine.