My 2000 Nissan Maxima has a PO430 code for the catalytic converter that has been going on and off for over 1 year now. My ? is, how would I know that the converter needs replacing? Someone said there wouldn’t be any smell necessarily, someone else said I would be leaking qts. of oil in between changes and someone else said it would get bad mileage. Each one debunks the others comments etc. Also just for info., this car had the ses light come on at 57K miles, my brother replaced 2 of the O2 sensors and I replaced 2 also, one duplicate one and a mass air flow as well.