BoilerFaultCodesVaillant D.002 Fault Code
Also written as D002 — same fault.
The Vaillant D.002 fault code means: this is a temporary pause where the boiler rests for a few minutes to prevent any unnecessary wear and tear from switching the burner on and off too frequently.. It appears on 10 Vaillant models in our database.
Technical description: Diagnostics code: Setting the burner anti-cycling time
What causes the Vaillant D.002 fault?
This occurs because the boiler has reached its required temperature too quickly and needs to pause before firing up again. It happens when the heat produced by the burner cannot be carried away fast enough, often because your radiators are already warm or the system's circulation is restricted. The boiler enters this brief rest period to prevent components from wearing out due to constant stopping and starting.
This is more common during the autumn and spring when the weather is milder and your home doesn't require the boiler's full heating power.
DIY fix possible
Wait 5 to 15 minutes for the countdown to endCheck that your room thermostat is turned upEnsure radiators are not all turned off
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Gas Safe Register →Vaillant models that show the D.002 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Vaillant D.002 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