Safety: Disconnect power before removing covers. Microwaves contain high-voltage components.

Clean the cavity: Grease and residue can coat the humidity sensor. Thoroughly clean the interior with a mild detergent and water (do not soak). Dry completely and test again.
Locate the humidity sensor: On many Whirlpool over-the-range models, the humidity sensor is mounted behind a small grille at the top of the cavity or behind the control panel.
Inspect sensor and wiring: Remove the control panel or top grille to access the sensor. Check for broken wires, loose connectors, or signs of moisture damage.
Replace humidity sensor: If cleaning does not clear the F4 code and the sensor or wiring appears damaged, replace the humidity sensor with the correct Whirlpool part.
Control board check: If a new sensor does not resolve the error, the control board's sensor circuit may be faulty and require replacement.

Microwave displays F4 and may stop sensor cooking functions

Possible Causes