Low
d.43 on Vaillant ecoTEC sustain

This code is simply an information display showing the current setting used to manage how much heat your radiators produce based on the outdoor temperature.

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.

What the manual says

Manufacturer manual

Heating curve: 0.2 to 4

From this model's manual
Verified against the Vaillant Ecotec Sustain installation & service manual, page 48.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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