BoilerFaultCodesVaillant F.XX-F.XX Fault Code
Also written as FXXFXX — same fault.
The Vaillant F.XX-F.XX fault code means: this code isn't an active fault but rather a menu view showing the history of past errors your boiler has experienced.. It appears on 13 Vaillant models in our database.
Technical description: Current value in list of faults (Lists are only displayed, and can only be deleted, if faults have occurred)
What causes the Vaillant F.XX-F.XX fault?
This code appears when someone has accessed the boiler's internal diagnostic menu to view a log of historical issues. It does not represent a new mechanical failure, but rather a digital record of errors that happened in the past. This is often used by engineers during a service to see if the boiler has struggled with things like low pressure or ignition issues over the last year.
DIY fix possible
Navigate through the menu using the plus and minus buttons to view the historyPress the 'reset' button to clear active faults if the boiler is currently locked outNo action is needed if the boiler is currently working correctly
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Vaillant models that show the F.XX-F.XX fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Vaillant F.XX-F.XX fault code information on this page is sourced and cross-checked against the official Vaillant service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026