Q: 2016 Ford fusion se grinding rear brakes only has 17000 miles

If the brake noise is occurring at all times, that is even without pedal application, then the caliper and/or torque plate are sticking or there is a parking brake malfunction. If the noise only occurs upon braking, it is most likely due to the use of aftermarket (not OEM approved) brake pads and rotors and is also sometimes attributable to failure to re-apply factory specified shims and/or appropriate anti-squeal compounds and lubricants. Unfortunately, once non-OEM parts and materials are used (if that has happened in your circumstance), and thus in essence an "experiment" is set up, brake noise can be a result. If there is a warranty, of course your first recourse is to simply return to the vendor and have them thoroughly address and permanently resolve this problem. Missing shims should be considered and the possibility of a lubricant solution should be considered. If the pads are non-OEM though and perhaps of low quality materials, for instance if they have lots of metallic chunks, such low quality pads will be inherently noisy. If the noise arises from pad material, really the only solution is to remove the pads and install the more appropriate OEM friction material (rotors should preferably be replaced with OEM rotors; you can try re-surfacing and/or de-glazing rotors though if any pad substitution is attempted). If you would like a YourMechanic professional to resolve this issue, please simply request a brake noise diagnostic and a certified mechanic will be dispatched by YourMechanic to evaluate your brakes and identify the root cause of the noise. Please let us know if you have further concerns or questions as we are always here to help you.