catalytic converter

a shop with a scan tool can graph the actions of the front and rear o2 sensors to see the condition of the cats. that will give you a good idea of what cat is bad. the reccomended replacement is factory which includes both cats as one which is very pricy. some shops will install aftermarkets or cut out and replace individual units. be carefull of these as they may not meet oem standards. ask for california certified cats only. Roy

first if you car has less than 80k its covered by dealer 8 yr or 80 k is cat warrenty ,,, and if your over and its rattling its done yes the whole cat