Low
D.040 on Vaillant ecoTEC Pro 24

Your boiler is measuring the temperature of the water flowing through it, but this code is just a status update indicating the current heat level rather than a fault.

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

Flow temperature actual value

From this model's manual
Verified against the Vaillant Ecotec Pro installation & service manual, page 43.
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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