Emergency
D.118 (16) on Vaillant ecoTEC exclusive

Your boiler has detected an electrical reading error within its internal safety monitoring system, meaning it cannot accurately check the exhaust gases.

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: Reference voltage too high

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.76View →

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