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04 outback not satisfied with new catalytic converter

engine light and flashing cruise control switch–computer says replace bank one—so I replace with factory catalytic converter----six months later light comes back on with flashing cruise control switch and computer asking me to replace bank one—So I use computer to shut light off----four weeks later light comes back on----called dealer they said “we usually replace both banks”—I found it most painful paying for dealer supplied catalytic converter even when I was under the impression that it would keep light off.—This is my wife’s car and she is not really buying the piece of black electrical tape I placed on dash over check engine light.—Am I dealing with a bad oxygen sensor ? Please help not having a happy life.

sorry for your pain, but I think you need a better analysis. Had a similar code in a different make but it ended up being o-rings in the plenum. I am not saying o-rings are the problem, could be a sensor but to find a mechanic that does not throw your money at could be is what you need.

There’s no such thing as a code that says “replace this part” or “replace that part”. You need to have a proper diagnosis done rather than just throwing expensive parts at the problem, hoping that something sticks.

Thank you Barkdog and mark9207 for your comments. The code that comes up is P0420 catalyst efficiency low bank one. I have searched this problem in the Cartalk Community. General opinion is that I should be trying to determine the cause of my "low efficiency ". Suggesting poorly running engine due to bad plug or plug wire , poor compression , or vacuum leak. Is there anyone who might have some experience with getting this code and could help me with what usually fix it? Let us all remember happy wife , happy life.

@alyourpal swallow your pride and pay a professional to diagnose the car

That is my advice. @Barkydog and @mark9207 concur, as you already know.

Or you can keep blasting your car with the shotgun until your wallet’s empty.

I’m not meaning to be rude, but sometimes it’s cheaper to pay someone to diagnose and fix a car rather than keep throwing parts at it.
I’ve worked on many cars that have been shotgunned before I got them. Usually the owners were really upset at themselves for having thrown new parts at it that did not solve the problem.

Don’t let this happen to you.

Other than agreeing with the advice you’ve been given I might add that if the first converter replacement apparently (?) solved the problem only to have it die 6 months later then that could be a sign of something killing the converter.
That could involve an engine performance problem, coolant from a weepy head gasket entering the combustion chambers on that side, etc, etc. A converter or O2 sensor has limits as to what it can help to control so replacing the converter could be looked at as an effort to cure the symptom and not the cause of the problem.

That’s all assuming the first converter was really on the fritz and the second also.