High
bxx on Keston C40

Your boiler has detected that the water inside the system has become dangerously hot or the water pressure is too low, causing it to shut down to prevent internal damage.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description

Overheat or water pressure lockout (first digit displays 9, followed by flashing error code starting with b)

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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