I tried Cataclean and all that stuff. Didn't work. Dave is correct. If something else is causing the cat inefficiency it will throw its own code. From what I read on the subject, the computer is comparing readings between the pre cat O2 sensor and the post cat O2 sensor. If the readings are not within range it throws the code.Thanks for the info guys. I reset the cel and put cataclean in the gas tank. But now the cel came back on after a gassed back up.