Microwave runs but stops after a few seconds and shows E04, or will not start and immediately shows E04.

Safety first: Unplug the microwave. Inverter-based microwaves use high-frequency high-voltage circuits that are dangerous to service without training.

• Check for obvious damage: Look through the vent openings for signs of burning or melted plastic. Do not insert tools or fingers inside.
• Power reset: Leave the unit unplugged for at least 10 minutes to discharge internal components, then reconnect and test. If E04 returns immediately, internal electronics are likely damaged.
• Avoid repeated restarts: Repeatedly trying to start the microwave with an inverter fault can worsen board damage.
• Service recommendation: Replacement of the inverter power module or main control PCB is typically required and should be performed by a Princess-authorized service center.