BoilerFaultCodesWorcester Bosch Lock-out Indicator Fault Code
Also written as LOCKOUTINDICATOR — same fault.
The Worcester Bosch Lock-out Indicator fault code means: your boiler has shut itself down for safety because it cannot successfully light or maintain a flame.. It appears on 1 Worcester Bosch model in our database.
Technical description: A flame failure device is incorporated into the control system... should the flame fail for any reason, or should ignition fail to initiate a satisfactory start, the boiler is automatically locked out for safety.
What causes the Worcester Bosch Lock-out Indicator fault?
This fault occurs when the boiler's internal computer can no longer detect a stable flame during the ignition process. The most common reasons are worn-out sparks that fail to light the gas, a dirty sensor that can't 'see' the flame, or an inconsistent gas supply preventing a steady fire from forming.
This fault is more common during the first cold snap of winter, as internal components like the gas valve can seize up after being inactive during the summer months.
DIY fix possible
Check if your other gas appliances (like a cooker) are working to ensure gas supplyEnsure your decorative gas fire or meter valve hasn't been accidentally turned offPress and hold the reset button for five seconds once gas supply is confirmed
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Gas Safe Register →Worcester Bosch models that show the Lock-out Indicator fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Worcester Bosch Lock-out Indicator 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