Noisy Kohler Faucet

I have a two year old Kohler kitchen faucet model K-12176 (Fairfax collection). Whenever I use the sprayer, the faucet makes a loud whining noise. Any ideas what could cause this and what the repair would involve? I've seen that parts are available on the Kohler site, but don't know where to start.
Thanks.

I would assume the diverter is fluttering. I would change that part out first.