Microwave beeps and shows E04; cooking will not start.

Safety: Unplug the microwave before removing any covers. Do not touch high-voltage components.

Cleaning and inspection:

• 1. Clean the cavity: Food splatter and steam residue can coat the humidity sensor. Wipe the interior walls and ceiling with a soft cloth and mild detergent. Pay special attention to the small sensor opening or grill (often on the upper side wall or ceiling) used by Sharp's humidity sensor.
• 2. Dry thoroughly: After cleaning, leave the door open for at least 30 minutes to allow moisture to evaporate. Excess moisture can cause false sensor readings.
• 3. Reset the unit: Plug the microwave back in and perform a power reset by unplugging for 2–3 minutes, then reconnecting. Try a manual time-cook mode (not sensor cook) to see if basic heating works.
• 4. Sensor wiring check (advanced): If E04 returns only when using sensor cooking, unplug the unit, remove the cabinet, and locate the humidity sensor module (usually a small PCB or sensor near the cavity wall). Check that its connector to the main control board is fully seated and that wires are not damaged.

When to replace: If cleaning and resetting do not clear E04, the humidity sensor itself or the control board sensor circuit may be defective. Replacement should be done with the correct Sharp humidity sensor part and may require a technician.