II - Low

Worcester Bosch II - Fault Code

Also written as II — same fault.

The Worcester Bosch II - fault code means: your boiler is performing a routine initial safety check to fill its internal drainage system after the power was recently switched off.. It appears on 3 Worcester Bosch models in our database.

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: Boiler running for 15 minutes at minimum heating output to fill the condensate trap (alternates with central heating flow temperature). This occurs if the mains supply has been interrupted.

DIY fix possible

Wait for 15 minutes for the cycle to complete automaticallyEnsure your heating or hot water controls are set to 'on'The code will disappear and be replaced by the temperature once finished

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Worcester Bosch models that show the II - fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Worcester Bosch II - fault code information on this page is sourced and cross-checked against the official Worcester Bosch service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 31 August 2026