I get the P0420 code ever 400 miles

[Butch-Explorer]

Hello everyone, I have a 06 Ltd Explorer 4.6 with 96000 miles. The coils were replaced last year but not the spark plugs. Would the plugs cause the P0420 code ? Truck runs great and gas mileage is ok. 11 mpg stop n go. 15 mpg city average / 22 - 24 mpg hwy @ 65mph.

 

[50hJoe]

The P0420 code is a catalyst efficiency code for bank 1 (passenger side), mean the PCM is seeing that this particular catalytic converter is not doing its job. It is possible that a misfire on that bank could give you that code. If you don't feel one or have any misfire codes then I would look for exhaust leaks and then check the O2 sensors on that bank.

 

[Butch-Explorer]

Thank you very much, will try that next.