It depends on what you mean by "bad"
If the converter is clogged up and you can not drive more then 30 mph then the converter is bad.
If the insides of the converter have broken up and rattle then the converter is bad.
As far as the converters function your car will tell you. The cars computer will listen to the oxygen sensors upstream and downstream of the converter and will be able to tell if the converter is still converting and then turn the check engine light on. The code set would be something like "converter no up to efficiency" or something like that.
If the converter is clogged up and you can not drive more then 30 mph then the converter is bad.
If the insides of the converter have broken up and rattle then the converter is bad.
As far as the converters function your car will tell you. The cars computer will listen to the oxygen sensors upstream and downstream of the converter and will be able to tell if the converter is still converting and then turn the check engine light on. The code set would be something like "converter no up to efficiency" or something like that.
