How do I mend a P0420?

They should yeah, but it really all depends on a lot of things like the overall health of the engine mostly. For example, my OEM cat went bad with under 50k miles on it which is wayyy to young for a catalytic converter to go out normally, but it was because the previous owner supercharged the truck and didn't do any supporting fuel mods which caused it to run lean. I also got a code for a bad rear O2 and had to replace it as well around the same time

But under normal conditions I think sensors and OEM cats should last well over 100k, but a cheap aftermarket cat I don't think I'd expect it to last that long. Really depends on the quality of the cat, the cheaper ones have less of the expensive material inside that filters the emissions so they die out more quickly.

 

well first you take that 420 and smoke it prob solved

 

go to a exhaust shop depending on where you live they can cut your old cat out stick in a new core weld it up in california there no longer allowed to do this so buy it off the dealer its about 1 grand or so i woulndt trust auto stores with a cat and or o2 sensors

 

Magnaflow sells CARB legal cats but you’re right - you have to get a legal one for CA unless your smog shop isn’t super careful.

 

yea cali sucks this law is new like 10 years new give or take.. befoer i paid 200 bucks they cut out my old core welded in a new one worth it then i got another vehicle and there all nope cant do it anymore.. its the same thing i mean a core is a core is a core same metals in it paladium gold etc etc california sucks now pepboys etc good luck they will fubar up that order iwould really go dealer only or Amazon or ebay.. but with amazon or ebay if its wrong you have to ship it back.. a pain in the ass.. so save up