Emergency
D.118 (12) on Vaillant ecoTEC exclusive

Your boiler has detected an inconsistency with its internal air quality monitoring sensor, meaning the system cannot confirm it is operating safely so it has stopped working as a precaution.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Act immediately

Turn off your boiler and stop using gas appliances. Call a Gas Safe engineer now. This fault can be dangerous if ignored.

Technical description

CO sensor fault number: Sensor plausibility test fault

Engineer required

This is a emergency 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.75View →F.61View →

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