BoilerFaultCodesVaillant D.93 Fault Code
Also written as D93 — same fault.
The Vaillant D.93 fault code means: your boiler's internal computer has lost its identity settings and doesn't know which specific model it is supposed to be.. It appears on 12 Vaillant models in our database.
Technical description: DSN appliance variant setting
What causes the Vaillant D.93 fault?
This fault occurs when the boiler's main control board loses its memory of which specific model it is installed in. The most common reason is that a new control board has been fitted but not yet programmed with the correct identity code, or an electrical surge has corrupted the board's internal settings.
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.93 fault code
Click a model for the full fault code list and model-specific repair notes.
- Atmomax Repair: £80-160
- ecoFIT Pure 418 Repair: £100-200
- ecoFIT Pure 425 Repair: £100-200
- ecoFIT Pure 435 Repair: £100-200
- ecoFIT Pure 825 Repair: £120-250
- ecoFIT Pure 830 Repair: £100-180
- ecoFIT Pure 835 Repair: £100-200
- ecoTEC Repair: £100-280
- ecoTEC 65kW Repair: £120-250
- ecoTEC Pro / ecoTEC Plus Repair: £100-200
- ecoTEC sustain Repair: £100-£200
- Home Combi Repair: £100-200
Source
Vaillant D.93 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 manual (PDF)
- Vaillant ecoTEC 65kW manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026