Microwave display shows E04 and unit will not start; interior light and clock may still function.

Safety first: Unplug the microwave before removing any panels. Avoid static discharge to the control board by touching a grounded metal object first.

Step-by-step checks:

• 1. Power reset: Unplug the microwave for 5–10 minutes to allow the control board to fully reset. Plug back in and test. If E04 returns, continue.
• 2. Inspect keypad surface: Check for liquid spills, cleaning fluid residue, or physical damage on the keypad. Gently clean with a slightly damp cloth and dry thoroughly.
• 3. Access control area: Remove the control panel mounting screws (often behind the top grille). Carefully tilt the panel forward.
• 4. Check ribbon cable: Locate the flat ribbon cable from the keypad to the control PCB. Reseat it by gently pulling it out and reinserting it fully, ensuring it is straight and locked.
• 5. Visual inspection: Look for corrosion or burn marks on the control board near the keypad connector.
• 6. If certain keys do not respond: The membrane keypad is likely failing and must be replaced as an assembly with the control panel fascia.

If E04 persists after reseating connections, replacement of the keypad or control board is usually required.