Low
S.40 on Vaillant ecoTEC exclusive Combi

Your boiler has detected a minor hiccup and is running in a limited mode to keep you warm while it monitors itself.

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

Product is in a temporary test mode or comfort protection mode (detected a temporary fault and continues to run with restricted comfort)

From this model's manual
Verified against the Vaillant Ecotec Exclusive Combi installation & service manual, page 42.
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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