Medium
N.343 on Vaillant ecoTEC plus Combi

Your boiler is struggling to accurately measure the air it needs for combustion, so it is running in a limited state to remain operational.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Book a service

This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

What the manual says

Manufacturer manual

The signal for the air-mass flow sensor is not plausible. If the sensor set for the air-mass flow is connected and there is feedback, but the values are implausible, the unit works in limp home mode.

From this model's manual
Verified against the Vaillant Ecotec Plus installation & service manual, page 95.
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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