Mechanics

DIAGONSTIC TROUBLE CODE P0420

2003 Toyota Corolla

Engine problem
2003 Toyota Corolla 4 cyl Wheel Drive Type unknown Automatic 88400 miles

I had a diagnostic test done at Autozone because my check engine light is on. The trouble code was P0420 or catalyst system below threshold (bank 1). Should I have the catalytic converter or the oxygen sensors replaced?
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Brian1994
December 18, 2007.



If the converter " bed" is broken up, you should hear rattling noise, try rapping on the converter to see if anything is rattling insde it. If so you will need to change the converter, muffler and connecting pipes.50,000 is the recommended 02 sesnsor lifespan, so change it anyway! If the cat melted, you will need to pressure test the exhaust, remove the 02 sensor before the cat, screw in the pressure gauge, take reading, if over 1/12 to 2 psi, replace cat!

Merlin2021
Dec 18, 2007.