CEL off and on
 

My 02S has thrown a code for insufficient cat converter function 3 times now, the same code comes up every time I believe it's p0143? The dash light will stay on for a few days then go out by itself. The car runs and idles fine either way. Any ideas? I've read that the cat converters themselves rarely go bad, the car has 101,000 miles.

Cheap enough to throw in a new O2 sensor post cat.