Ok so I got a SES light and its for bad precats, I don't remember the code exactly, but I do know its for at least one of the precats. Around that same time my exhaust (which is pretty old, and pretty rusted) started being really loud and obnoxious, it has a really loud drone to it, especially at 2k rpm's. I don't know if bad cats would cause this!?! I didn't think so, but they both came up at around the same time. My friend it sounded like there was a hole in my exhaust, or maybe a really big leak, which would make sense b/c my exhaust is pretty rusted.

 

what cause what?
getting louder = leaks
having codes = sensors or cats

 

how many miles on the car? Im assuming its the 2001 se you have in your profile.....

 

It just hit 100k miles, i'm pretty sure its the original exhaust :/, except for the muffler which was replaced like 30k miles ago.