P0420

[Hemi44]

I have a 2005 Dodge Ram 1500 5.7.
171K miles

P0420 code came on so I replaced O2 sensors. Code came back on a day later. I replaced the wires, plugs and coils and it stayed off for about 3 days then came back on. So I'm guessing replace the Cat Converter??

 

[Later2u]

I've done this mod on my commuter 2001 Maxima.
I used one non-fouler because I have a lathe and was able to bore it out to fit the O2 sensor and still have the little hole on the end.
Worked like great.

 

[LeesEvoX]

Also check for exhaust leaks. This can gives you that code

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