2011 Toyota Sienna 2GRFE 106k P0420

[Thermo1223]

Yes the dreaded or maybe not depending on the repair catalyst below efficiency code. Came on for a short stint then went off on it's own.

One of my employees just purchased it after a garbage truck totalled her Kia Soul. It seems like a strong runner engine & transmission wise. Lots of power but a slight tick dependant on RPM. IMO it's either a leaking exhaust manifold gasket or maybe valvetrain. Really only audible with the radio & hvac off and even at that faint. It certainly could use shocks/bushings etc...but that's not my deal.

I am sure many a BITOG has had this engine or van so just looking for is it worth replacing the O2's or not.

 

[Accent Abuser]

If the exhaust manifold is leaking that will cause a p0420. You need an actual scan tool to graph the downstream oxygen sensor, if it's capable of averaging a steady .45v or higher the cat is probably good.

I'd also check long and short term fuel trims, and do a cylinder balance test, a rich or lean cylinder can completely screw up the fuel trims and cause the converter to malfunction. For example, I had a lean condition in cylinder 2 due to a bad injector causing the lambda sensor to command a higher fuel delivery across ALL cylinders. Of course that means 3/4 cylinders are rich, that set a p0420 code, fixing the injector problem fixed the cat code.

Basically the very last step after resolving any AFR problems is to then replace the converter. Converters don't go out on their own generally, they're ruined by AFR problems that are let go too long.