New engine last week, now P0420 code (understanding O2 sensors)

[44nyholm]

Hello all, fresh engine is doing well but it did get a p0420 yesterday. The engine, and all components are new. Bank 2 sensor 2 is reading .1 and only fluctuates with gas. The other 3 02 sensors are fluctuating normally. Time for new cats? Anyway to test the cats with them being conjoined?

 

[ItchyDong]

Graphing the 02’s is the best way to view its function.

Here’s an excellent video on how to troubleshoot.

 

[44nyholm]

Graphing the 02’s is the best way to view its function.

Here’s an excellent video on how to troubleshoot.

Watching the graphs... bank sensor 1 fluctuates and bank sensor 1 downstream mimics it. Bank 2 upstream fluctuates but bank 2 downstreams hovers from .06 to .120 at idle and then fluctuates/mimics when I give it gas. If I'm understanding this correctly, bank 1 cat is bad. All of the sensors have been swapped with known working units that I keep on hand, and I can't hear any exhuast leaks either. I love living in CA and paying more for cats.

 

[ItchyDong]

Yeah that sounds like it’s dead.

 

[44nyholm]

Yeah that sounds like it’s dead.

Fwiw, it was dead. The two upper ones. Thanks for the help