BoilerFaultCodesKeston E09 Fault Code
The Keston E09 fault code means: your boiler has detected an internal communication problem between its electronic brain and the gas supply system, meaning it cannot safely light the flame.. It appears on 9 Keston models in our database.
Technical description: Valve drive error - possible gas valve or control box fault.
What causes the Keston E09 fault?
This fault occurs when the boiler's main control board loses the ability to communicate with or operate the gas valve safely. The most common reason is an electrical failure within the gas valve's motor or a fault on the circuit board that prevents it from sending the correct starting signal. In some cases, it can be caused by loose or damaged wiring connections between these two vital components.
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 E09 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Keston E09 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