E09
Siemens Communication Error Between Control Boards

Microwave shows E09 and will not accept input or start programs.

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Safety Warning

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

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Possible Causes

Loose harness between user interface board and main control board, failed main PCB, failed display/keyboard PCB, firmware communication fault

How to Fix / Troubleshooting

Safety warning: Disconnect power before removing any trim or accessing internal boards.

Steps to try:

  • 1. Power reset: Unplug the appliance or switch off the breaker for 10 minutes. Restore power and check if E09 clears.
  • 2. Check for surges: If E09 appeared after a power outage or surge, consider using a surge protector in future. The board may already be damaged.
  • 3. Inspect display behavior: If the display is blank or garbled along with E09, the user interface board may be faulty.
  • 4. Technician-level: Remove the control panel, inspect the ribbon cable and connectors between the display PCB and main control PCB, reseat connectors, and test. Replace the main control PCB or UI board if communication cannot be restored.

Because this involves low-voltage control electronics, professional diagnosis is recommended.

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Repair Difficulty

Hard 4/5

Required Part

Main Control PCB
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