So I recently had my engine replaced in my 2003 V6 4Runner and I still keep having a check engine light pop up for the P0420 and P0430 codes for the catalytic converter bank 1 which I believe is on the passenger side. I’m moving across the country in 2 weeks and my mechanic had me put this CRC emissions system cleaner in the gas tank thinking maybe the cat is clogged with debris from when my head gasket blew and it just has left over crap in there and he said that it may clean it out. I replaced the engine because it was gonna take longer than I had to rebuild the engine. Is this stuff legit or should I just have the cat on the passenger side replaced or try and replace the O2 sensors first?


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One code is bank 1 and the other is bank 2 so you have it for both sides. There is a cat in each of the exhaust manifolds then a 3rd downstream after both exhausts tie together. First thing I'd check is if you have an exhaust leak near the cats, typical place is where the left side attaches to the right side. You can also have a leak where the exhaust manifolds attach to the heads but doubtful that would give you codes for both sides. There are tons of threads for these codes with fixes being all over. Here is a thread from another site will similar issues on a Sienna. It gives good detail on how it works.

P0420 & P0430 Fixed For Less Than $20 | Toyota Sienna Forum - siennachat.com

I’ll definitely try this I talked to my mechanic and he said as long as the engine is running fine I should be good but I’ll try to clean the MAS with some iso alcohol. I already have a nice K&N air filter I probably need to clean it so hopefully that works.


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