Microwave displays E4 and beeps; turntable may rotate but no heating occurs.

Safety first: Unplug the microwave before removing any covers.

• Clean the interior:
  • Wipe down the entire cavity, especially the area near the vent or sensor grill (often on the upper side wall).
  • Use a mild detergent and warm water; avoid spraying directly into vents.
• Reset power: After cleaning, leave the door open to dry, then unplug the unit for 5–10 minutes and reconnect.
• Locate the humidity sensor:
  • On many Black+Decker models, the humidity/steam sensor is mounted behind a small grill inside the cavity or near the top front.
  • Remove the outer cabinet and locate the small sensor module connected by a harness to the control board.
  • Check for loose or corroded connections and reseat the plug.
• Test sensor-dependent modes: Try AUTO COOK or SENSOR REHEAT. If E4 appears only in these modes, the sensor is likely defective and should be replaced.

If E4 persists after cleaning and reseating connections, replace the humidity sensor module or have a technician diagnose the control board.