How do I know which catalytic converter needs replaced?

Question

There is 3 on this vehicle.

Answer 1

What you have on this vehicle is a front left catalytic convertor , a front right catalytic convertor, and a rear three way catalytic convertor. , this vehicle has 4 oxygen sensor the front is the upstream these are the engine management sensor , these are sensor 1. when you set a catalytic convertor code it is the downstream 02 sensor that  monitor the catalytic convertor. these are Sensor 2. This vehicle only has 2 code for a catalytic convertor. A P0420 this would be for Bank 1 catalytic convertor, Bank 1 is where cylinder 1,3,5 are located. this is the right side, If you set a P0430 this would be for Bank 2 this is the left side where cylinder 2,4,6 are located. There is no downstream  02 sensor that monitor the rear three way catalytic convertor, To find out if that is defective the use of a temperature probe, or the use of a scantool data stream as long as the downstream 02 sensor reads above .650 mlvts you have a good working catalytic convertor. when its below that for a period of time this is where the ECM see it as below efficiency.