Will the diagnostic tool that plugs into the O2 sensor tell me if the cat is stopped up or not working right? I was going to take my truck to the dealer and have them check this to rule it out or in for causing problems.

 

if it's throwing a service engine code and that code is related to a bank 1 or bank 2 - Sensor 2 then that would be an indication that either the sensor is bad or the catalytic converter is bad. If it's not throwing a code a basic code scanner won't do anything for you.

 

I am trying to find a way to determine exhaust backpressure with no codes. I want to know if the cat is bad or good.