Q: car needs to be smogged

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i just got the check engine light checked and it came up with p0420 catalyst system efficiency below threshold bank 1 the mechanic said it was the Catalytic converter. How much would it cost to fix/ would it need to be looked at again for them to know and would it be able to be smogged after this fix?

My car has 170000 miles.
My car has an automatic transmission.

Hi there. When the oxygen sensors have a reading that is similar to each other, it is an indication that the catalytic converter is not working as efficiently as it is intended. If the voltage of the downstream oxygen sensor decreases, and begins to fluctuate like the upstream oxygen sensor, it means that the oxygen levels are too high and the Power Control Module will then store the P0420 trouble code. This can be caused by cracks in the exhaust system, faulty O2 sensors, worn out catalytic converter or even high fuel pressure or faulty fuel system components. Due to the multiple possible sources, it’s best to have a professional mobile mechanic come to your location and complete a check engine light inspection, so they can pinpoint what is causing this trouble code to illuminate and recommend the right repairs that will help you pass emissions in your state.

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