Low
d.09 on Vaillant Home Combi

This code is not actually an error; it simply displays the target heating temperature currently requested by your smart thermostat.

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

HeatingflowsettargettemperaturethatissetontheeBUSroomthermostat

From this model's manual
Verified against the Vaillant Home Combi installation & service manual, page 31.
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 your room thermostat settings to ensure the target temperature is set to your preferenceNo further action is required as the boiler is operating normally

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