Q: Got P0420 code and I had the catalytic converter replaced but still have the code. What is going on?

asked by on November 02, 2017

I have a P0420 code on my car. I had the catalytic converter replaced as well as the O2 sensors, but I still get the P0420 code. What is going on?

My car has 177000 miles.
My car has an automatic transmission.

The code P0420 can be caused by the catalyst, O2 sensors before and after the catalyst. If both O2 sensors and catalyst was replaced then you may have an exhaust leak at the manifold or pipes. I suggest you have a mechanic like one from YourMechanic do a complete diagnostics of the code and inspect for any exhaust leaks to isolate the cause of the code returning.

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