Microwave beeps and shows E3, will not start a cooking cycle

Safety first: Disconnect the microwave from power before any internal inspection.

• 1. Clean the cavity thoroughly: Food splatter and steam residue can coat the humidity sensor window. Wipe the interior walls and ceiling with a mild detergent solution, then dry completely. Pay special attention to any small grill or opening where the sensor is located (often on the upper side wall or ceiling).
• 2. Power reset: After cleaning, leave the unit unplugged for 5–10 minutes to allow the control board to reset. Plug back in and test an auto-cook or sensor program.
• 3. Inspect sensor area: If accessible without removing the cabinet, visually inspect the sensor cover for cracks or heavy discoloration. Replace the cover if damaged.
• 4. Internal sensor check (advanced): With the cover removed and the unit unplugged, locate the humidity sensor module (small PCB or sensor near the cavity wall). Check that its wiring harness is firmly seated on both the sensor and main control board. Look for corrosion or burnt spots.
• 5. If E3 persists: The humidity sensor or the control PCB sensor circuit is likely defective. Replacement of the sensor module is the first step; if that fails, the main PCB may be required. These repairs are best handled by a service technician.