BoilerFaultCodesKeston E25 Fault Code
The Keston E25 fault code means: your boiler's internal computer has encountered a critical error and cannot safely operate the system.. It appears on 9 Keston models in our database.
Technical description: Control box errors - possible faulty control box.
What causes the Keston E25 fault?
This fault occurs when the boiler's internal computer brain fails to communicate correctly with the safety sensors and ignition components. It is physically caused by a microchip failure or a corrupted circuit on the main control board, preventing the boiler from managing the heating process safely. The most common reason is general electronic wear and tear or a power surge that has damaged the delicate internal wiring.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Gas Safe Register →Keston models that show the E25 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Keston E25 fault code information on this page is sourced and cross-checked against the official Keston service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026