Intermittent P0420 Check engine - Catalytic Converter replacement?

Fix the oil burning issue that is causing it to go bad and then try whatever snake oil in a bottle to revive your cat.

Spoiler alert: The Prius is built to CARB emissions standards. Putting in a Federal/EPA cat will eventually trigger the 420 again.

 

It takes the muffler guy about 30 minutes to weld in whatever you bring him realize it aftermarket catalytic converters are not going to have as much material inside of them that's what the factory deems necessary for the Prius so you may never get the light off or it may go off for a minute and be playing the games is playing with you now If you live in an emissions state then you have to deal with this I don't and I don't.

 

I would get a better cat that has worked for many. A Walker 16337.


There is no way to clean a clogged cat, especially on the car using an additive.

 

You can try it I've heard people swear by it I don't have emissions where I live so what's the least of my worries One of my cars has no catalyst in the whole plumbing system oh well funny thing when it's put on an exhaust gas analyzer it sniffs as clean as a new one or a new one of that year model It's in the spec I think that's pretty funny My old Corollas did the same in Massachusetts gut the catalytic converter put it back up in place. Take it in for the sniff test passes with flying colors thank you bye.

 

You are good to go I lived in Western Massachusetts during the years where I wouldn't have been good to go for sure or they had the tailpipe sniffer and all that nonsense late '70s early '80s and down here where I am we don't have emissions doesn't matter the year of the car in the county I live in so I don't have to do anything check engine light can be on they don't even care what the codes are they don't even look My car I get to honk the horns flop the turn signals and they might look at the tires and make sure there's no white light leaking from rear colored lamps and that's it so basically the same as you.

 

No chemical way to clean a cat on or off the car. Passing inspection is not the only reason to replace a cat. A clogged cat will keep the check engine light on which may hide another serious issue. A clogged cat can reduce performance and efficiency. A really bad cat can damage the engine. Some might remove a bad cat and straight pipe it for the last concerns but you would still have a check engine.

 

I've read some possibly-promising things about circulating a heated citric/oxalic acid solution through it off the car. Have had no occasion to try it, though.

Depends what's wrong with the cat, of course. It may reportedly help if the honeycomb surfaces are fouled, impeding the catalytic reaction. Doesn't help if the honeycomb is melted into a blob, impeding exhaust flow.