Usually a defective cat will not cause the car to die while driving. It would be great to know which engine you have in your car, the V6 or 4 cyl, because the Catalytic Converter set ups are different. Many of these cars have a pre-cat right off the manifolds, called a warm up cat and then they have a main cat farther back. Do yo have a check engine light, if so, then get the code. If you have a bad cat you will have a P0420, 421, 422 etc type of code. If you car is dying, often this is a defective crank sensor, but make sure that your get the code(s) first.
My 2003 Sonata had the secondary catalytic converter clog up because the primary converter was running too hot and got brittle, broke and sent pieces down to clog up the secondary cat. after running it that way for months.
The car shut down on highway after loss of power. It would go about 100 yds. after a 5-10 min. rest. After the 2nd 100 yd. jaunt, it would not start and I had it towed to shop. Mechanic said the cat. was clogged up, so he showed me, after removing cat., that it started up and ran fine, but loud. He picked up the cat. on end and tapped it on floor to show me the pieces that come out which clogged it. Therefore, the new cat. was installed and the car ran fine for about 5 weeks before the chk. engine light came back on.
Previously, the check engine light was on but gave misfiring codes for months. No one ever said that your cat. might get burnt up if you don't stop the misfirings which I was trying to do anyway. Did all the recommended things: changed plugs, wires, coils and treated gas with injector cleaners. The check engine light stayed on. No one told me,initialy, that there were two cat.'s on the car, so I didn't think that I had a bad primary cat. which was the case and I was still getting misfirings. If they had changed the primary cat., it may have gotten damaged like the last one due to misfirings which continued.
I said to myself, after doing all the recommended actions, maybe it's the injectors, so I took the out and one was damaged. I replaced that one and all orings on the others and the misfirings stopped. The bad news was that I still had the chk engine light go back on, but this time it was the P0421 code referring to an inefficint catalytic converter Bank 1 or Pirmary. I am installing this now and hope my problms are over and the light will not reappear so I can finally pass emissions. I've had cars that have not run, as well as, this car that passed emissions all the time, very frustrating! Good luck.
