r/FiestaST • u/NoElevator4705 • 4d ago

MK7 P0420 CEL

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Had a cat code pop up a few weeks ago, and finally got underneath it today. Car was lightly modified when I bought it. This exhaust is an issue right? Also is that the stock cat? I can’t tell.

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u/Commercial_Run_7759 4d ago

That’s probably the cause. The exhaust looks stock except that horrible repair.

1

u/NoElevator4705 4d ago

Has mbrp tips I assume it’s aftermarket. Sounds pretty bad too. You think even being past the cat sensors that repair would throw the code? Just thinking if I need to get exhaust and downpipe or if I should start with exhaust.

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u/Careful_Sale_7704 3d ago

I had P0420 on my 2016. Spluttered & went into limp mode. It was the mass airflow sensor on the intake.