BoilerFaultCodesWorcester Bosch P1 Fault Code
The Worcester Bosch P1 fault code means: your boiler is repeatedly trying and failing to complete its ignition process, essentially getting stuck in a loop during startup.. It appears on 13 Worcester Bosch models in our database.
Technical description: Boiler indicates start-up sequence (Start sequence not completed if it restarts at P1)
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.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Worcester Bosch models that show the P1 fault code
Click a model for the full fault code list and model-specific repair notes.
- Greenstar 2000 Repair: £120-200
- Greenstar 25 HE Combi Repair: £90-160
- Greenstar 25HE Repair: £120-350
- Greenstar 25i (ZWB 7-25) Repair: £200-500
- Greenstar 27CDi Repair: £120-200
- Greenstar 28CDi Repair: £120-200
- Greenstar 8000 Repair: £120-200
- Greenstar CDi Compact Repair: £0-80
- Greenstar R29 40 HE
- R30 HE Plus Repair: £0-120
- Ri 25 HE Repair: £120-220
- Worcester 25/30 HE Repair: £90-180
- ZB 7 27 HE Repair: £200-450
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.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026