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Discussion Starter #1
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!

Cheers,
Jonathan
 

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Discussion Starter #2
UPDATE: I swapped the downstream sensors (driver to passenger side and vice versa) then cleared the DTC. My code reader also has O2 sensor testing as an option. The tests produced identical results for both upstream and downstream sensors on both banks so I think it must have been a poor terminal connection. While both connectors seemed to be fully seated, I took care to listen and feel for a positive "click" when connecting the terminal ends. No new trouble codes yet. The driver-side "bolts" (seized nut on stud) seemed loose too but I don't think a downstream exhaust leak would produce a fault. Still no driveability/performance issues with several days of city and highway driving.


Cheers,
Jonathan
 
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