BoilerFaultCodesKeston C2 Fault Code
The Keston C2 fault code means: your boiler’s internal computer chip has encountered a communication error or is missing, preventing the system from running safely.. It appears on 8 Keston models in our database.
Technical description: Boiler Chip Card (BCC) fault
What causes the Keston C2 fault?
This fault occurs when the boiler's main control board loses its connection with the small plug-in memory chip that tells the unit exactly how to operate. The most common reasons are a loose connection due to vibration, a malfunction within the chip itself, or a hardware failure on the main circuit board that prevents it from reading the chip's data.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Keston models that show the C2 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Keston C2 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