Microwave display shows E04 and unit will not start a cooking cycle.

Safety first: Disconnect power before removing any panels.

• Step 1 – Power reset: Turn off the breaker or unplug the microwave for 5 minutes, then restore power. Sometimes E04 can clear after a control reset.
• Step 2 – Check for stuck keys: Press each button on the Thermador keypad firmly. If any key feels stuck or does not click, the membrane may be damaged.
• Step 3 – Inspect ribbon cable: Remove the control panel assembly (usually a few screws behind the trim). Carefully disconnect and reconnect the flat ribbon cable between the keypad and the electronic control board to ensure a solid connection.
• Step 4 – Dry moisture: If the panel was exposed to steam or cleaning liquids, allow it to dry completely for several hours with power disconnected.
• Step 5 – Replace faulty component: If E04 persists, replace the membrane keypad or the complete user interface panel. If still unresolved, the main control board may need replacement.

Note: Avoid spraying cleaners directly on the control panel; apply to a cloth first to prevent future failures.