would a bad 02 sensor throw a cat. conv. code? and shut the car down?

What is your question?

I've replaced the cat. conv. twice in the past year. Now, the car is not running, codes throwing for cat. conv, o2 sens, knock sens, lean running... By the time I figure out whats ruining the cat. converts I'll have spent WAY more than the value of that car. I'm a single mom, college student and drive ALOT! Time to trade in?