How do I know which catalytic converter on my 2016 Kia Soul needs to be replaced?

How is there an assumption that the catalytic converter is a concern? I would be looking at engine performance diagnostic testing to find out what is going on. By the way, I'm only seeing that your car has one catalytic converter for what it's worth -- but I wouldn't guess at that for repairs. Expensive guess. www.repairpal.com/repair-shops