2013 Sienna rattling noise caused by the almost detached heat shield located over the muffler. Three out of the four holding points were broken, causing one end of the shield to fall on the muffler, resulting in the rattling noise due to the vibrations of the muffler when the engine is running. Easy fix, I think. We'll see how long it lasts. Let the exhaust line cool down before you perform any repairs. Use all the necessary precautions. If you decide to do any repairs yourself, you will be doing at your own risk. Consult with your mechanic or service center before you proceed.