how can i test a converter while it is still on the car?

Does it smell like rotten eggs or not?

Thats pretty much it without going to a professional shop. If it does, yours is shot. Other wise you need to take it off and inspect it.

Does it smell like rotten eggs or not?

Thats pretty much it without going to a professional shop. If it does, yours is shot. Other wise you need to take it off and inspect it.
thanks guy will have to check with the owner its not my car just trying to help a friend again thanks for the input and will let you know what i find out