Q: The Check Engine light is on. I know the vehicle needs a new catalytic converter.

If someone has already diagnosed that the catalytic converter is faulty on your vehicle and you know they are correct, that is the cause of your check engine light. Your oxygen sensors pick up more fuel in the exhaust when your catalytic converter is clogged therefore causing rich codes. Once the catalytic converter is replaced and the check engine light is reset it should not reappear unless another separate issue occurs.