I have had this car for just over 25k miles. This sound started when I was purchasing the car and the dealership told me it was just the heat shield. At that time the noise was tiny and could barely hear it. Now after miles have been driven it can get fairly loud at times and hard to pin point where it exactly is coming from. I did post a video and with sound up the rattle is possible to hear. It’s not a consistent noise either.

 

Sounds similar to what was going on with mine a few years ago. In my case, the cat material had broken apart into chunks and was rattling around inside. Only real fix is replacement.

 

Where you getting a code for a bad cat? I have a code occasionally but it’s just for an o2 sensor.

 

No code for me. I also don’t think I drove it like that very long. I don’t doubt that this issue could cause a code to be thrown.