I have a 2004 toyota sequoia with 280,000 miles on it and cde has come with deficiency in my catalytic converter.
I was hoping that Lacquer thinner won't hurt my car but it's got so many miles on it...
I presume you have a P0420 or P0430 code. If so, please see under FAQ for what to look for. Lots of things can cause that code, it’s not always the catalytic converter itself.
How to fix a bad catalytic converter?
Replace it. However first make sure that's the actual problem, and if it is you should figure out why it failed (oil burning, too rich mixture, etc.) and fix that problem or the same thing will just happen again.
I'm guessing your check engine light is on? It's ill-advised to put lacquer thinner in your gas tank. Take the catalytic converter out of the vehicle and immerse it overnight. Catalytic converters are self-cleaning if the engine is running properly, so your engine has some kind of problem.
Usually the only fix, assuming it is a bad cat, is to replace it. @Justin-shepherd has a good recommendation to try before replacing it.
How to fix a bad catalytic converter?
you replace it, and then fix what fouled the cats.
But run some O2 sensor diagnostics first.
