BoilerFaultCodesWorcester Bosch LOCKOUT LIGHT FLASHING Fault Code
Also written as LOCKOUTLIGHTFLASHING — same fault.
The Worcester Bosch LOCKOUT LIGHT FLASHING fault code means: your boiler has stopped working because it failed to light or stay lit, which has triggered a safety shutdown.. It appears on 4 Worcester Bosch models in our database.
Technical description: Burner Lockout. Possible causes: gas supply issue, spark electrode/lead failure, gas valve failure, flame sense electrode/cable failure, or control board fault.
What causes the Worcester Bosch LOCKOUT LIGHT FLASHING fault?
This fault occurs when the boiler tries to light the burner but fails to detect a stable flame after several attempts. The most common reasons are a lack of gas reaching the unit, worn-out spark components that can no longer create a flame, or a sensor that is too dirty to 'see' the flame once it has started.
DIY fix possible
Check if your gas supply is active and credit is on your meterPress the reset button once to see if the boiler restartsEnsure any external gas valves are in the open position
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Gas Safe Register →Worcester Bosch models that show the LOCKOUT LIGHT FLASHING fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Worcester Bosch LOCKOUT LIGHT FLASHING fault code information on this page is sourced and cross-checked against the official Worcester Bosch service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026