BoilerFaultCodesKeston E31 Fault Code
The Keston E31 fault code means: your boiler has lost communication with the internal sensor that monitors the temperature of the water leaving the unit, usually due to a loose wire or a faulty part.. It appears on 9 Keston models in our database.
Technical description: Flow sensor open circuit – check connections to flow sensor are in place
What causes the Keston E31 fault?
This fault occurs when the boiler's main control board loses the electrical signal from the sensor that monitors the temperature of the water being sent to your radiators. The most common reason is a physical failure of the internal thermistor or a loose connection in the wiring that prevents the system from safely tracking heat levels. Because the boiler no longer knows how hot the water is, it shuts down as a safety precaution to prevent overheating.
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 E31 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Keston E31 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