Low
d.00 on Vaillant ecoFIT pure

This is a setting that limits how hard your boiler works for heating to save energy and match your home's size, rather than a broken part.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

Technical description

Heating maximum output

DIY fix possible

Navigate to the installer level menu by pressing the 'Menu' button.Find 'Diagnostic codes' or 'd.00' in the display settings.Adjust the kilowatt (kW) value up or down to suit your home's heating requirements.

Find a Gas Safe engineer
Search the official register →

Related fault codes

d.01View →d.02View →

Related guides you might find useful

Is boiler cover worth it?

Break-even maths on monthly cover.

Read →

When to replace your boiler

7 signs repair isn't worth it anymore.

Read →

New boiler cost 2026

Realistic UK prices for a swap.

Read →