Safety first: Unplug the microwave before removing any panels. Avoid contact with the high-voltage section.

Step 1 – Power reset: Disconnect the microwave from power for at least 5 minutes to allow the control board to fully discharge. Plug it back in and check if E04 clears.
Step 2 – Check for moisture or grease: Inspect the control panel area for signs of moisture ingress (from steam) or heavy grease buildup. Wipe the exterior with a slightly damp cloth and dry thoroughly.
Step 3 – Inspect wiring harness: With power disconnected, remove the control panel assembly and check that all harness connectors to the main PCB are fully seated and free of corrosion or burn marks.
Step 4 – Board evaluation: Look for obvious damage on the PCB such as burnt spots, cracked solder joints, or swollen components. If present, the board must be replaced.
Step 5 – Replace control board: If a wiring issue is not found and E04 persists, replace the main control board with the correct Bertazzoni part number for your model.

Firmware-related faults and relay failures generally require board replacement rather than component-level repair.

Microwave beeps and shows E04; keypad and display respond but cooking will not start.

Possible Causes