BoilerFaultCodesWorcester Bosch P1 Fault Code
The Worcester Bosch P1 fault code means: your boiler is struggling to start up because a small internal fuse has failed, which prevents the electronic control system from receiving power.. It appears on 11 Worcester Bosch models in our database.
Technical description: Please wait, initialisation in progress. 24 V fuse blown.
What causes the Worcester Bosch P1 fault?
This fault occurs when the boiler begins its ignition sequence but fails to establish or maintain a stable flame within the required time. The most common reasons are worn-out spark electrodes that can no longer create a spark or a faulty gas valve that isn't delivering enough fuel for the fire to light. Because the system cannot confirm the presence of a safe flame, it constantly resets to protect itself.
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 P1 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Worcester Bosch P1 fault code information on this page is sourced and cross-checked against the official Worcester Bosch service / installation manuals for each affected model.
- Worcester Bosch 537i manual (PDF)
- Worcester Bosch Greenstar 25 HE Combi manual (PDF)
- Worcester Bosch Greenstar 25HE manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026