Removing The Serpentine Belt:
To remove the serpentine belt, the automatic belt tensioner must be rotated to relieve the tension on the belt.
To rotate the tensioner, I inserted a 3/8" drive ratchet into the square hole and pushed the ratchet to the left (arrow). Then I slipped the serpentine belt off the idler pulley.
I found it best to start with the ratchet handle straight up, because when the belt is removed the tensioner will rotate back, and the wrench handle can hit the water pump pulley, making it impossible to remove the wrench.