[FirstYorkie]

I REALLY don't think that his lack of response to treats is a dominance issue. Many dogs aren't food motivated, especially if they are free fed.

Personally, I would still look for a treat that excites him more - probably human food. A tiny bite of steak or liver, maybe. A cheerio. A lick from one of those squirt cans of cheese. Also, if he doesn't have hypoglycemia issues, I wouldn't free feed him (if you are).

Does he have a favorite toy? Perhaps you could bring that out as a reward to be played with only when he potties.

Or, maybe the freedom to sniff is what he finds most rewarding. If your yard is fenced, perhaps the reward for pottying is that he immediately gets unleashed to sniff to his heart's content.

In other words, I would like for what your dog finds most rewarding and figure out how to use that.

Also 4 months is still pretty young. Don't give up - it may take a bit longer.