Great question and in fact there is a test which tests the Catalytic Converter specifically. It's called the CAT Intrusive Test. A smog repair station will take an exhaust sample before and after the CAT. It's called "intrusive" because most often they need to drill a small hole before the CAT to get the pre-CAT sample. This test will show the CAT's efficiency.
You may run into the only problem of a smog station not willing to simply conduct a CAT test without testing the entire emission system. Typically smog failure diagnosis runs about two labor hours. The average labor hour should cost $60 to $70 dollars.
posted by SmogTips Support 01-31-2012 09:47 PM