-ll- Low

Worcester Bosch -ll- Fault Code

Also written as LL — same fault.

The Worcester Bosch -ll- fault code means: your boiler is performing a routine internal safety check to ensure internal water levels are correct and will return to normal operation automatically within 15 minutes.. It appears on 2 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: Trap filling programme is active. The appliance remains at minimum heating output for 15 minutes to ensure the condensation trap is filled.

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Worcester Bosch models that show the -ll- fault code

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

Source

Worcester Bosch -ll- 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 27 April 2026