Thread: o2-cat code question.

P0420 is a code that that computer throws when it determines the catalytic converter is not functioning properly. The computer reads the second O2 sensor and uses this reading to tell if the cat is doing it's job. Most of the time that will be a bad cat or an aftermarket cat that is not doing as good of a job as the factory one did. My car kicked a P0420 code after I put on the headers and high flow cat.

In your case. U should be fine. Its more than likely the high flow cat that's throwing the code. It flows more than stock. So the computer sees diff readings. All u can do is get a stock oem cat or have that code set to non report via a tuner.