45 -- 45 Low

Worcester Bosch 45 -- 45 Fault Code

Also written as 4545 — same fault.

The Worcester Bosch 45 -- 45 fault code means: your boiler is currently running in a restricted low-power mode, likely because it is performing a specific system test or an automated diagnostic check.. 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: Continuous working at the minimum sanitary/heating power (Special programme visualisation)

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 45 -- 45 fault code

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

Source

Worcester Bosch 45 -- 45 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