On Wed, 10 Aug 2016 06:54:00 -0700 (PDT), Frank Thompson
wrote:

Side by side Whirlpool refrigerator is cooling only to 58 degrees when set to lowest setting. Serviceman replaced diffuser, but that did not remedy the problem. Freezer side is working fine. Any suggestions appreciated.

.... unplug the power cord for 5 minutes

Reboot the unit :-)