I am getting engine smell inside the cabin of the car. Check Engine light is on on 2001 Toyota Corolla

Mechanic told me that it was catalytic converter. I had it replaced sometime ago and engine is light still on. Him guessing trying to figure out what the problem was got too expensive. Now after driving the car with engine light on, I know smell engine in the cabin.. which is very strong and I have to drive with windows open. Please help

Asked by for the 2001 Toyota Corolla