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Q: Should I replace or clean the catalytic converter?

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I was told I have a bad catalytic converter my car is not displaying any of the symptoms of bad converters but the engine check light is on so should I try a cat cleaner first?

My car has 165000 miles.
My car has an automatic transmission.

Hey there. The Check Engine Light can set if the catalyst efficiency is below threshold. There will be no visible symptoms at all, or change in engine performance, because the recorded "low efficiency" can simply mean that more pollutants are being emitted in the exhaust rather than destroyed or "converted" in the catalyst.

So to perceive a difference you would need a gas analyzer to measure what is going on with the tailpipe emissions. Before trying a catalytic cleaner (which itself is problematic if you have a particular product in mind, ask the manufacturer if they have any written, independent laboratory test evidence that it actually works. If they have nothing in hand to send to you, don’t waste your money), the pre- and post-O2 sensors have to be tested in order to determine whether the catalyst has really failed. There is a specific test strategy using output from those two sensors that has to be employed; an exhaust gas analysis is useful as well. If you need help having this checked, a certified professional from YourMechanic can come to your car’s location to diagnose the car and can replace the catalytic converter if necessary.

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