Thread: o2-cat code question.

noobish question but, i have a p0420 catalyst efficiency below thresh hold bank one. which o2 is this? or is it the cat. my first assumption was the front o2 sensor. but advance says its a bad cat. its a 05 n/a with 140ish k miles on it.

I've got that, but haven't dealt with it yet, I think its the one before the cat

I had the same P0420 code come on at 100,000 or so on my 03 GT. A local shop put in a new cat and an 02 sensor. The code away for about 1 yr and came back. Shop put in another o2 sensor for free, but the light came on a week later. Shop put in another cat for free, and the light came back a few months later. Problem was the aftermarket cat was not doing a good enough job.

Permanent fix was a piece of black tape over the light.

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.