Fix what? It doesn't look broken in the picture you posted. Is it cut, is it 'open'? Is it just insulation off the wire? Fix it is fine, this involves covering it if insulation is missing, splice if broken OR a complete opening of the harness and pulling it out to its other end. How deep do you want to delve into it is entirely up to you. Good luck with whatever is wrong with it. So far, I am not sure exactly what is wrong with that ground since the picture isn't clear enough and so far your explanation is vague.

.