BoilerFaultCodesVaillant d.6 Fault Code
Also written as D6 — same fault.
The Vaillant d.6 fault code means: this code is not actually an error; it is simply showing you the temperature your boiler is currently set to reach for your hot water.. It appears on 2 Vaillant models in our database.
Technical description: Hot water temperature target value in °C
DIY fix possible
Recognise that this is a status code rather than a faultCheck your boiler display settings if you wish to adjust your target hot water temperaturePress the 'i' button on your boiler control panel to return to the normal operating display
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Vaillant models that show the d.6 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Vaillant d.6 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 7 July 2026