ive had the infamous p0420 code for about a year now. i notice if i ride my car for high periods of time at high speeds (highway) it will go away soon there after. a mechanic i know told me that its possible to burn out the pre-cats (super heat the pre-cats and the carbon just dicinigrates) if you run your car like this. if this guy is BSing me then is there any reason why my code will go away and come back at random times?
FOR SALE: 2002 Chevy Caviler, 34,000 miles, 6500. check out the classifieds
99 SE ATX
89xxx miles still running strong
| 
