CEL code '05 Subaru Impreza

[Seguino]

So the check engine light came on and I borrowed a code scanner from a guy at work and here's what it tells me.
P0420 Catalyst efficiency below threshold
Freeze frame data:
Fuel System 1 CL
Fuel System 2 CL- Fault
Calc load % 24.71
ETC ˚F 186
STFT B1% 2.34

So can someone decipher this info for me? Is fuel system 2 the downstream O2 sensor?
It's $100 to plug it in at the dealer, so if this info points to a specific thing that would be grand.
Needing a new cat would actually be the best case as it's still under warranty!
Thanks in advance for your suggestions.

 

[StevieC]

If you are sure you don't have a plugged converter, I.E. Converter is running red hot with poor exhaust flow out of the tail pipe then it is most likely your downstream oxygen sensor. (After the Catalytic one)


How is the fuel economy and power? I have seen the upstream ones cause a problem like this and we kept replacing the downstream and it turned out to be the upstream because the computer was referencing the 2 of them. (Rare problem though)

 

[gathermewool]

If you post on nasioc.com (subaru forum)in the maintenance section you might get more help. If the fault is referring to the DS sensor, then it just needs to be replaced. If it's referring to bank 2, then the fault is there because subarus only have one bank. If the scanner can tell you open loop, closed loop status, plug it in and check. If you don't see it switch to closed loop a minute or two after a cold start or if it switches to open loop while cruising, then it's probably the DS O2 sensor that needs to be replaced

 

[Seguino]

So, after three attempts to have the dealer do a driving test ( CEL has to be on to test and twice it literally shut off pulling into the dealer's lot! ) the good news is that the cat is toast. Yes, this is good news as the cat is still under warranty.
The dealer said I should change the O2 sensors when the cat is replaced. I don't have a problem with that, except that the price for the OEM sensors is just shy of eight hundred bucks! I can get Denso sensors for about one sixty or NTK for two forty.
Anyone have experience with these sensors as opposed to OEM? One of these companies probably makes the Subaru sensors.
Thoughts?

 

[The_Eric]

Our shop has had very good luck with the Denso First Time Fit O2's.