BoilerFaultCodesKeston L2 Fault Code
The Keston L2 fault code means: your boiler has lit correctly but the flame has gone out unexpectedly, often due to a fuel supply issue or a blockage in the condensate pipe.. It appears on 8 Keston models in our database.
Technical description: Flame loss
What causes the Keston L2 fault?
This fault occurs when the boiler successfully ignites but cannot maintain a steady flame, causing the system to shut down for safety. The most common reasons include a temporary interruption in the gas supply, a dirty internal sensor that can no longer 'see' the flame, or a blockage in the drainage pipe that causes water to back up into the heat exchanger.
This fault is frequently seen during freezing winter spells, as the Keston's external condensate pipe can freeze solid, preventing the boiler from clearing waste fluid.
DIY fix possible
Check that your gas emergency control valve is open and you have credit on your meter.Check if the condensate discharge pipe (the plastic pipe leading outside) is frozen or blocked.Reset the boiler by pressing the 'Restart' button.
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Gas Safe Register →Keston models that show the L2 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Keston L2 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