P0420 Bank 1 Error Code.. Need part #'s

[Compton]

Hi,

I apologize in advance for asking this, but I have seen conflicting information about this on this board and other boards.

My 2005 Murano FWD (w/ 140k miles) is spitting out P0420 Bank 1 error messages. I am going to replace the spark plugs (about 60k miles old) and O2 sensor first. If that doesn't work, I am going to replace the cat as well. Can someone please verify which part #'s I need to order from rockauto.com? (My mechanic will be doing the actual work)


O2 Sensor: Do I need:

1. DENSO Part # 2344301 (Downstream)

OR

2. DENSO Part # 2345060 (Upstream)

OR With 140k miles, does it make sense to just go ahead and replace both of them?

Catalytic Converter: Do I need:
1. MAGNAFLOW Part # 50219 (REAR)

or

2. MAGNAFLOW Part # 50218 (Front)

Thanks a lot.

[nitely]

Cross match the denso to the oem...2004 Nissan Murano Engine Control Module - 22661