Q: I'm getting a po420 code the car is losing power. What are the odds it's the cheaper rear cat?

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I'm getting a po420 code the car is losing power. I've changed the downstream sensor no luck. What are the odds it's the cheaper rear catalytic converter? There are no sensors after the rear cat. I'm hoping there's a chance it could still be that one. The front one is welded to the manifold and a lot more money to replace.

My car has 103000 miles.
My car has an automatic transmission.

Hi Jason. When the oxygen sensors have readings that are similar to each other, it is an indication that the catalytic converter is not working as 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 Powertrain Control Module (PCM) will store the P0420 trouble code. It might be a good idea for you to read this article on the P0420 OBD-II code, as it will provide you with several ideas as to the possible sources and repair solutions to consider.

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