Low
d.11 on Vaillant ecoTEC sustain

Your boiler is simply reporting that a secondary pump, responsible for circulating water through your heating system, is currently not running.

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

Status of the heating circuit's shunt pump: off/on

From this model's manual
Verified against the Vaillant Ecotec Sustain installation & service manual, page 47.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

DIY fix possible

Check if the room thermostat or heating controls are calling for heatMonitor the display to see if the status changes when heating is activatedNo action is typically required as this is a status indicator, not a fault

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