High
F.334 on Vaillant ecoTEC Plus 836

Your boiler's computer system has lost the specific settings that tell it how your exhaust pipe is configured, preventing it from starting up safely.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

What the manual says

Manufacturer manual

Flue system configuration not completed. The configuration of the flue system was not completed.

From this model's manual
Verified against the Vaillant Ecotec Plus installation & service manual, page 90.
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 is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Related fault codes

F.33View →F.34View →

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