What doesOBDII code P0420 2003 corolla mean?

Answer 1

I have the same fault code on my 2003 Corolla. From my research, the code means that the car's computer is sensing that there has been a drop in catalytic converter efficiency. This is determined by the computer by comparing the signal of the O2 sensor mounted before the catalytic converter with the signal of the O2 sensor mounted after the catalytic converter. If the two signals are too similar, this means that the catalytic converter is not doing it's job. A number of things can be the cause of the fault code:

# Bad catalytic converter - It's reached the end of its useful life. It's time to replace it. # Engine leaks oil and/or coolant into exhaust- Oil and/or coolant is leaking and is clogging the catalytic converter. Engine seals and gaskets should be checked. Engine compression should also be tested. Any leaks should be repaired and the catalytic converter should be replaced. # O2 sensor/s bad - Although O2 sensor failure usually gives it's own fault code, not everything is perfect. Sensor's should be checked anyway just in case the computer did not catch the fault. In this case sensor/s need replacing. I hope this information comes in handy. Unfortunately, what ever your specific situation is, it is most likely a costly one.