Help diagnosing P0420

Stop blowing ganja smoke by the air filter, the ethanol is already bad as it is.

 

I would fix that first, or take it off and see what's being it, perhaps a crack in the manifold or something.

 

I removed it and cleaned the whole thing thoroughly. I think my next move will be take it all out and spray the whole exhaust system w soapy water.

 

Time to replace the cat (I think the 97s only had one?) if you haven't identified an exhaust leak before the sensors.

I also chased this code for awhile and new cats was the only thing that made it go away for good. I live in CA and have to have 50 state legal cats as well, Maganflow makes good quality ones for much less $ than OEM. Still pricey though especially these days.

In 2016 when I got them they were $600 installed but I wouldn't be surprised if they are double that now.

 

I had similar issues on my exhaust (but no codes). Started with my header cracking... common on Tacomas (used the soapy water/cold pipes method to find crack and replaced with OEM). Then my rear O2 sensor and muffler rotted all the way through (replaced both). Finally my cat gaskets started leaking... and at that point I just replaced everything cats, gaskets and hardware. My whole system is OEM new from the headers back. Was expensive AF but I had read many other people having problems trying to piece meal their exhaust system with new and old parts.

 

My 2004 3.4L P0420 code was due to the cats. Once I replaced them, with ones from Magnaflow, the code has been gone since. Think it was around $800 for the cats, and then $150 for installation.