Thermador · Oven / Range
E121 Pro Recommended Thermador Oven E121 — Control Board Communication Error
Part of the control panel stops responding and some cooking modes disappear.
Updated July 2026
What does Thermador E121 mean?
The main oven control unit lost communication with a secondary board (e.g. the user interface or the relay board). Multiple cooking functions may become unresponsive.
What causes Thermador E121?
- Loose ribbon cable between control boards
- Power surge affecting one or both boards
- Failed control board
How to fix Thermador E121 yourself
- 1 Turn off the oven at the circuit breaker for 2 minutes, then restore — power cycling clears most transient communication faults.
- 2 If the display shows E121 immediately after power restore, it is a persistent hardware fault.