BoilerFaultCodesWorcester Bosch FD231 Fault Code
The Worcester Bosch FD231 fault code means: your boiler has shut down because it lost power while it was already trying to deal with an internal safety error.. It appears on 3 Worcester Bosch models in our database.
Technical description: The mains voltage was interrupted during an interlocking fault
What causes the Worcester Bosch FD231 fault?
This fault occurs when your boiler loses its electrical connection at the exact moment it was trying to handle a separate internal safety issue. It effectively means the boiler's computer has become confused and entered a protective shutdown because it couldn't finish its safety check. The root cause is usually a loose connection in the wiring or a failing electronic control board that can no longer process power signals correctly.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Gas Safe Register →Worcester Bosch models that show the FD231 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Worcester Bosch FD231 fault code information on this page is sourced and cross-checked against the official Worcester Bosch service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026