my question characters were more than 10 why iam i getting this message
code cat efficency below threshold installed universal cat still hve same code on 2000 Toyota Corolla
p0420 code is that the converter is the efficency of the converter the catalytic converter is the last part to be checked and replaced.first a road test of the car must be done is the engine running ok is there a misfire then check for cav. leaks check for worn spark plugs and ignition wires check fuel filter is not blocked check engine oil level check mass air flow sensor alot of times dirt gets on air flow sensor wire check 02 sensors the front sensor should allway be moving up and down while the rear sensor should stay steady if all that checks ok then the convereter should be checked 1 with a heat gun the rear part of the converter should be 30 to 40 percent hotter also check for broken parts in converter. if the converter is the cause then you will need to use a toyota part a after market part will not work.