I have a 2002 Hyundia Accent 1.6L & in NC I had 2 failed points: 1) Catalyst NOT READY 2) Evaporative System NOT READY. I disconnected the battery last Saturday to clean corrosion from the battery posts & have driven the car 250 miles since then. The car has 34248 miles, what could be wrong?

Engine has to be cold start the vehicle with the engine cold do not turn the engine off drive to the nearest hayhway and drive for 50 miles at 55 to 65 mph steady driving that shoult solve your problem 100%

I have never heard of such a thing over my 35 yr span. Try a Hyundi dealer. I believe with that low of milage, if it was bought new as a left over, like May of '02 you may get Hyundi to pay for the converter and labor. (10 yr emissions warranty). You just need the original in service date. (date first bought by retail buyer). If you can, talk with Hyundi service dept and get their advice and terminology and post me back. Also ask @ the emissions warranty. It stays with the car, not the orig. owner(s).

Im not 100% on what that means but a catalyst is what is inside your catalyctic converter which is an emmission control system along your exhaust line sounds like there may be something wrong with your exhaust system hope that helped