Q: Code p0421, but new catalytic converter installed. Worried it's placed too far back in the system.

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I had a new exhaust installed with no catalytic converters. I had an exhaust shop weld a new one in, placing the second o2 sensor after it. I have the wires extended but it still throws a code. I'm worried the converter is too far away from engine and the first sensor.

Hi there. Due to the fact that you’ve completed aftermarket alterations to your Mazda, you are likely going to continually have error code problems as you’ve indicated. The ECU is calibrated to receive data from OEM designed exhaust systems. Since we’re unable to provide aftermarket service repair advice, I would recommend working with the exhaust shop or a Mazda service professional to find a solution.

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