engine light still on on 2005 Toyota Corolla

change everything plugs air fliter oil change front and back o2 sencers drove from god nos were its sayin on my freind machice it passes but engine light still on and i no i got to get it inspected their not gonna pass it

2 answers 1 comment
P0420 is low catalytic converter efficiency code. Usually a sign that the cat. converter is failing. This code can be set if the engine is out of tune or the Oxygen sensors are not operating correctly.
what code is stored??

Roy
p0420