Tips on Buying Cars: used car (hidden problem), toyota corolla, good car

Question
I live in New Jersey. I bought a car from a dealer. (99 toyota corolla) I tested the car and everything seemed fine. I was aware of some of the problems and I accepted it that way. When I took it to a mechanic to get them fixed, he also told me that somehow "check engine" light was shut off and told me that my catalytic converter had to change. This seems to me like a total fraud. I am thinking of filing a claim to the court but I just wanted to know if it is the right approach or am I screwed no matter what I do.  

Answer
Generally speaking, used cars are sold "as is".  The time to have a mechanic check the vehicle is before, not after the purchase.  
Just because the vehicle has issues doesn't necessarily prove that the selling dealer had knowledge of the same. But, even if they did, an "as is" used car is what you likely bought.

I don't know about New Jersey, but most dealers in the south where I'm from would still try to help you out with this.  

At least be happy that you bought what is generally a very good car and once you've gotten these things taken care of, you'll likely get many years of service from the Corolla.