Remove fridge lower pane. De-iced pane with fan, and evaporator with hair dryer. Measured evaporator sensor with ohmmeter. Was open, high impedance. Ordered replacement part, along with the upper fridge main sensor, in case needed later. Called customer service to clarify sensor PN. Shawnia was very helpful. She sent schematics with troubleshooting info. Very useful.
Re-assembled the fridge with bad part; waited for the new parts to arrived; de-iced again replaced sensor, after confirming it had the correct impedance. Re-installed panes.