Just looked up the diagram and its pretty straight forward, Passenger fuse box on the top left and is the only relay in the panel youll beable to see.
As an experiment on a day you dont need your wipers swap it with the relay for your wipers, Its the relay closest to the center of your under hood panel. if the problem goes away suspect the relay. All gm vehicles made in the last 15 years have the same relays so it shoudl be easy to find.
It looks like this,
Google Images
Let me know if this helps
