BoilerFaultCodesPro L Fault Code
The Pro L fault code means: your boiler has stopped working to protect itself and is waiting for you to check a secondary code to find the specific problem.. It appears on 1 Pro model in our database.
Technical description: Boiler is in lockout for a specific error. Display will be blinking, alternating with a number or letter to show which error is detected.
DIY fix possible
Check the display for a flashing number alternating with the 'L' codePress and hold the 'Reset' button for 3 secondsCheck your gas supply and boiler pressure if the reset does not work
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A cover plan would handle faults like L: no call-out fees, no surprise bills.
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Pro models that show the L fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Pro L fault code information on this page is sourced and cross-checked against the official Pro service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026