BoilerFaultCodesKeston C0 Fault Code
The Keston C0 fault code means: your boiler's internal memory chip is not communicating correctly with the main control board, preventing the system from starting up.. It appears on 8 Keston models in our database.
Technical description: Boiler Chip Card (BCC) activation fault
What causes the Keston C0 fault?
This fault occurs when the boiler's main control board cannot read the data from the small memory chip that tells it exactly how to operate. This is usually caused by a loose connection where the chip is plugged in, or a physical failure of the chip’s internal circuitry after years of heat exposure.
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 C0 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Keston C0 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