see post #2 for the recommendation. If you avoided the dealership like the original poster possibly has, you could end up spending more money, just throwing parts at the car. The dealership scanner would be able to show the real code, and then maybe lead to a proper diagnosis. What would happen if you spend $800 on a new cat, installed it and then the fault comes back, when the cause of the fault was due to a software error. You have to look at all the different components, not just the search button. But it could be any of the following problems

1)fuel quality
2)software error
3)o2 sensor
4)cat converter