What F40 Means
F40 means the control board has lost communication with a secondary module, commonly the display or a sensor control board.
Common Causes of F40
- Loose or damaged wiring harness between boards
- Failed secondary control board
- Failed main control board
🔧 One Safe Check You Can Try
Try a full power reset at the breaker — a communication error that clears and doesn't return may have been a temporary glitch.
⚠ Why You Shouldn't Go Further Than That
- Confirming which board has actually failed requires testing communication between them, and ordering the wrong one is an expensive guess.
Opening a panel to inspect or repair something yourself doesn't automatically cancel your manufacturer's warranty — but it can risk accidental damage, and some manufacturers do have specific service conditions. Check your product's warranty terms, or ask us, before deciding.
Technical Reference
- Code
- F40
- Appliance
- Miele dryer
- Maker documentation
- Miele owner manuals and use & care guides
- Checked
- September 2026
Code meanings can change between control generations. Before acting on a code, match the full model number on your appliance's rating label against the manual for that model. We are an independent repair service, not affiliated with Miele & Cie. KG.