I have a 2012 Ford Focus with a P0420 code. I want to upgrade the exhaust system, but I can’t find a high-flow catalytic converter or good headers.
Any suggestions?
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My gf’s 2012 Focus has the same issue, and I’m not sure what to replace it with. something like MagnaFlow if i’m not wrong
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The problem is, Ford doesn’t like non-original parts. I’m seeing the same code, which first appeared a while ago, got cleared, and then started showing up more often.
carried out research on how to fix it properly. I can make it appear less often, and it only shows up about once a month or every 1,500 km.
If you want to pass emissions tests, a Euro4 catalytic converter should work. You can replace the cat with a Euro4 one and then have a tuner remove the post-cat lambda sensors from the ECU. This way, you won’t see the code anymore.
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Have you checked your exhaust yet? The stock headers are already quite short, and remember, 4-cylinder engines don’t scavenge exhaust like V engines do. The stock catalytic converter also seems to be pretty high-flow.
As you mentioned, MagnaFlow might be your best bet for an “upgrade,” but don’t expect a big difference.
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Ah got it. Thank you
the P0420 code can be fixed with a simple upstream O2 sensor replacement. I haven’t had the code or any issues since. I hope this helps 
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Will the upstream change it? I thought it wouldn’t make any changes. I updated the downstream, but it’s still there.
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Are you experiencing any additional codes???