2002 Toyota Corolla catalyst efficiences below threshold

2002 TOYOTA COROLLA
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MLSMC
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Computer problem
2002 Toyota Corolla Automatic 157000 miles

I have this check engine code: catalyst efficiences below threshold
and I am told to put gas treatment in my tank and it may fix the problem. Is this good information?
Dec 9, 2008 at 8:14 AM
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MMPRINCE4000
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It is more than likely a bad O2 senor(s). Especially if they have never been changed.
Before changing them have a backpressure test performed on the CAT to see if it is clogged or partially clogged.
Dec 9, 2008 at 9:09 AM