2011 Nissan Sentra p0420

I have a 2011 Nissan Sentra. It has had the following codes for 1.5 to 2years.
Primary DTC P0420
Secondary DTC P0430
Catalytic converter below threshold bank 1
I feel no loss in power. It idles a little rough but not bad. Would it be the O2 sensor or catalytic converter? Any help appreciated.
I also saw that a miss fire might cause this issue. I have new plugs and wires ordered.

A bad O2 sensor will set an O2 sensor code.

A bad cat will set a cat code.

Evey vehicle I’ve had in the shop with a P0420 DTC turned out to be because of a bad cat.


1 Like

Dam, I was hoping it wasn’t a catalytic converter. Oh well thank you very much for your help.

Everybody does when the computer displays the dreaded P0420 DTC.


I went to change the spark plugs. From left to right spark plug wells

#1 had a lot of oil.
#2 dry (No oil)
#3 oil residue
#4 practically full of oil

I’m planing on changing the valve cover gasket and well seals.
This would cause a the engine to not run efficiently. Could this be the culprit of the P0420 code or could it have cause my catalytic converter to go bad?

Misfires definitely don’t help, in regards to catalytic converter longevity

But my gut feeling is your catalytic converter has degraded to the point where P0420 set

Definitely no exhaust leaks?

P0420 usually sets and the car “feels fine” . . . fwiw

1 Like

Have someone connect a scanner to the vehicle to monitor the O2 sensor after the cat to determine if the cat is bad.


1 Like

I will have it tested and reply with the results thanks