I bought this 2014 ES for my daughter's 2 weeks ago and been monkeying with car doing basic maintenance.
I apologize if this has been discussed previously but I heard this rattling noise under the car during acceleration when I first drove the car and I figured it's just something is loose no big deal. The wife drove the car yesterday and the noise really bothered her (she's been driving a very quiet BMW i3) and told me to get rid noise asap.
Got under the car today starting from the back tapping, shaking things and when I got under the steering rack I shook the 2 brake lines right above the steering rack and noticed them loose inside the metal bracket. I zipped tied both lines to the bracket to stop them from moving. When I did that I was not sure if it was the culprit but it seems like it fixed the problem. Hopefully the rattling noise is gone for good.