Bad (new) O2 Sensor? P0430
Today (Monday 25 Feb 2019) my truck (2001 Toyota Tundra, Access Cab, Limited, 4.7L, TRD 4x4 with 269250-miles) threw a check engine light reported as P0430 on the diagnostic code reader. I believe P0430 is bank 2 (passenger-side) sensor 2 (downstream, after the catalytic converter). But this isn't as straightforward as a CEL and DTC perhaps.
Before the CEL came on today, the fuel economy had been mildly declining (at about 13.4mpg right now in combined hwy/city driving) so I had decided to replace the oxygen sensors which I actually installed on Friday (22 Feb 2019). There have been zero drivability/performance issues -- perhaps the exhaust smelled a bit rich but that is debatable. During removal and re-installation, the studs for the rear sensors did pull out from the exhaust (meaning the nut is seized to the stud making it into a bolt essentially...I applied anti-seize to the threads before re-torquing). I used brand new Denso 234-4162 (downstream) and DENSO 234-4169 (upstream) sensors but other than that there were zero issues. I already pitched the old sensors and the new sensor packaging. I can't believe the catalytic converter coincidentally failed a few days after replacing oxygen sensors.
I've come up with three options but I'd like any informed opinions that don't include replacing the catalytic converters:
(1) Should I tighten the current (new) passenger-side downstream sensor? Did the anti-seize perhaps allow a poor seal? Would a leak here even set a trouble code?
(2) Should I swap the passenger-side downstream sensor with the driver-side downstream sensor and clear codes to see if the fault returns on bank 1?
(3) Should I just replace the seemingly-faulty passenger-side downstream sensor? It's about $50 for the sensor and I might be able to replace it.
Thanks for any productive advice!
LTC Jonathan D. Howell, CSEP, PMP, USA, Ret.