What would cause honda hrv rattling noise?

A rattling sound in a Honda HR-V could be a number of things. One of them is a problem with Your ball joints. It could also be that there is an issue with the sway bar links in the car. Another one to look out for are the struts and strut mounts. Some people experience rattling sounds when accelerating. This is more likely to be a result of low fluid levels in the car. Topping up the fluids can possibly resolve the sound. Check Your transmission fluid by pulling out the dipstick under the hood and looking at the stick. If it is low, then add more to it. If that doesn't fix the sound after driving it around for a bit, then it might be something else.