BoilerFaultCodesVaillant d.01 Fault Code
Also written as D01 — same fault.
The Vaillant d.01 fault code means: your boiler is currently running its internal pump longer than expected to move residual heat away from the heating element, which is usually a normal safety feature rather than a breakdown.. It appears on 18 Vaillant models in our database.
Technical description: Water pump over run
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Vaillant models that show the d.01 fault code
Click a model for the full fault code list and model-specific repair notes.
- ecoFIT Pure 418
- ecoFIT Pure 425
- ecoFIT Pure 435
- ecoFIT Pure 825
- ecoFIT Pure 830
- ecoFIT Pure 835
- ecoTEC plus aquaPLUS
- ecoTEC sustain
- Home Combi
- Home System
- Thermocompact
- Turbomax 824/828
- Turbomax Plus
- Turbomax Plus 824/828E
- Turbomax Plus 828
- Turbomax Plus 828 E Repair: £120-250
- Turbomax Plus VUW 242E
- Turbomax Plus VUW 242EH Repair: £120-200
Source
Vaillant d.01 fault code information on this page is sourced and cross-checked against the official Vaillant service / installation manuals for each affected model.
- Vaillant ecoFIT Pure 835 manual (PDF)
- Vaillant ecoTEC plus aquaPLUS manual (PDF)
- Vaillant ecoTEC sustain manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026