Microwave stops and displays E04, often when using grill or combination modes.

Safety warning: Internal live parts and hot surfaces can cause shock and burns. Allow the appliance to cool fully and disconnect power before any inspection.

Steps to try:

• 1. Cool-down: If E04 appears during grill use, open the door, unplug the unit, and allow it to cool for at least 30 minutes. Then reconnect and test a short grill cycle.
• 2. Check ventilation and installation: Ensure the built-in Siemens microwave has correct cabinet ventilation cut-outs as specified in the installation manual. Poor airflow can cause grill overtemperature.
• 3. Observe grill operation: With a safe, empty metal rack (if supplied) and no plastic items, start a short grill cycle and look through the door. The grill element should glow red after a minute. If E04 appears and the element never glows, the grill circuit may be open.
• 4. Avoid blocked top area: Do not place foil or large flat dishes directly under the grill that could trap heat against the ceiling.
• 5. Technician-level: Test grill element resistance, check the grill NTC sensor values, and verify continuity of the thermal cut-out. Replace the grill element or sensor as needed.

If E04 repeats, professional diagnosis is recommended to prevent overheating damage.