My Yorkie has just recently decided this week that he no longer wants to have anything to do with the grass. He refuses to go outside to potty, and if I pick him up and put him outside he will either potty on the porch or sit at the door and not go at all(When put in the grass he darts back to the porch). Then minutes later inside he will go on the carpet. Within this past week he has not only used the carpet but also mine and my husband's side of the bed, the couch and his kennel where he sleeps! Everytime he puts his head down and knows he did wrong!!! I just do not understand nor do I know what to do, Please Help!
Your dog might not be scared of the grass, but might have developed an allergy to it. Check the dog's paws for redness and see if after being outside she tends to itch, sneeze, eyes water etc. My mother's dog is allergic to the type of grass most common in her area. She has learned to take one step off the porch/sidewalk, do her busy and get back on the porch. We helped her out by clearing a section of the backyard of grass and she spends most of her time there.
Another thing could be how tall your grass is. Yorkies are small and the grass could just be at an uncomfortable highth for her. Try cutting a section very short if you think that might be the problem.
Last but not least it might be that she/he had a trauma using the bathroom on the grass. My maltipoo peed on a fireant hill once resulting in bites in a very tender area. She was noticeably skittish about going outside for a while after that.