Low
S.55 on Vaillant ecoTEC exclusive

Your boiler is undergoing a mandatory safety check of its internal air quality sensors and is briefly pausing to ensure it is operating safely.

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.

Technical description

Waitingtime:COsensor | Waitingperiod:COsensor

DIY fix possible

Wait for the countdown to finish as this is a normal self-testEnsure there are no obstructions to the flue terminal outsideIf the code persists for more than 15 minutes, try a manual reset

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Related fault codes

S.54View →S.56View →

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