Earlier today, my SES light came on. Had diagnostic scan and it pulled up a code P0430, catalyst system efficiency below threshold (bank 2). Would this be from a bad converter??? My exhaust started rattling the other day and now I've got this code. Anyone know what this could be from???
Thanks!!

 

sounds like a bad cat to me. Guy came into work and came up with a similar code. Fixed his cats and code went away!

 

Either a bad cat or rear O2.

 

bad cat had the same problem 5 monthes ago.