Diagnosis
The upper spray arm on this model is fed by a water diverter that directs pressure either to the lower arm or the upper arm/middle sprayer. Weak or no spin up top means a clog in the arm itself, or the diverter isn't sending water its way.
How to Fix It
Remove the upper rack. Unscrew the upper spray arm (it usually just twists off its post). Check all the spray holes for clogs—use a toothpick or thin wire to clear them. Also, look down the center post hole for debris. Soak the arm in vinegar if there's scale buildup. Before reattaching, manually pour a cup of water down the center feed tube to make sure it's clear.
If That Didn't Work
If the arm is clean but still weak, the diverter motor or mechanism might be faulty. You can sometimes hear a whirring or clicking sound as it tries to shift. A failed diverter won't send enough water pressure upstairs. Testing and replacing it involves removing the inner door panel.
Heads Up
Don't use detergent pods if you have this issue. The plastic pod casing can sometimes get lodged in the diverter or feed tubes. Switch to gel or powder temporarily to see if the problem clears. Also, ensure the lower spray arm isn't obstructed, as that can affect overall system pressure.