JennAir microwave displays F4 and will not run; often related to humidity or temperature sensing.

Safety First: Disconnect power before accessing internal components.

• Locate humidity sensor: On many JennAir microwaves, the humidity sensor is located behind a small grille inside the cavity or near the top of the oven interior.
• Inspect sensor area: Remove any food debris, grease, or residue around the sensor opening. Clean gently with a mild detergent and a soft cloth, then dry thoroughly.
• Check connections: Remove the outer cover (if required by your model) and inspect the sensor wiring and connector for corrosion or loose fit. Reseat the connector.
• Test sensor: With a multimeter, check the resistance of the humidity sensor or thermistor according to the tech sheet values. An open or shorted reading indicates failure.
• Replace sensor: If the sensor is defective, install a new humidity sensor or cavity thermistor designed for your JennAir model.
• Control board check: If a known-good sensor still results in F4, the electronic control board may be faulty and require replacement.