Hey Scotty,
I recently purchased an 05 Subaru outback 3.0 liter H6 L.L bean edition. about a week into driving it a noticed the check engine light came on and the cruise control was blinking. I ran the code at autozone and it came up as a p0420 code. I've used cataclean twice and it only did the trick for a couple of days. Do you think this is an O2 sensor issue or a bad catalytic converter.
Thanks,
Justin B
I would suspect a crudded up 02 sensor. You could try cleaning it but if it's the pre-heater circuit, I would replace it.
The down stream one is about $50 and the upstream one is about $100.
The catalytic converters for that car are very expensive, there is one for each bank and they cost $400 to $500 each. (That's for EPA compliant converters - if you're in the Peoples' Republic and need CARB compliance you're looking at more like $1600 each. Prices from rockauto.com.)
So while I'm not a fan of the parts cannon approach it would probably be worth replacing the Bank 1 O2 sensors to see if the problem clears up. Be sure to use OEM sensors, not aftermarket. (Probably Denso or NTK on that car.)
Thanks for your feedback, I'm going to a local mechanic to have him diagnose the system. Ill post an update after
As usual, Chuck has the best answer.