my son drives 02 civic. 1.7 auto . It is showing 2 check engine codes, one for knock sensor, one for cat converter , I forget exact term, he has noticed that the engine doesn't provide much heat inside the car unless it is driven and mileage has been down some. I feel the knock sensor has failed, engine is not operating efficiently, and has caused the converter to set a code also. Mechanic tells him that the converter need replacement, and somehow it is responsible for knock sensor code... I think how is that? Is this B S ? Thanks