BoilerFaultCodesWorcester Bosch 306 Fault Code
The Worcester Bosch 306 fault code means: your boiler is still detecting a flame even though it has tried to shut off the gas supply, which is a safety conflict.. It appears on 10 Worcester Bosch models in our database.
Technical description: Flame signal after closing the fuel supply
What causes the Worcester Bosch 306 fault?
This fault occurs when the boiler's internal sensor detects a flame or an electrical current that looks like a flame even after the gas has been told to turn off. The most common reason is a gas valve that hasn't fully closed or an ignition electrode that is sending a false signal back to the main control board.
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 306 fault code
Click a model for the full fault code list and model-specific repair notes.
- 1000 Repair: £150-300
- Greenstar 2000 Repair: £150-300
- Greenstar 27CDi Repair: £150-300
- Greenstar 28CDi Repair: £150-300
- Greenstar 4000 Repair: £150-300
- Greenstar 8000 Repair: £150-300
- Greenstar 8000 Life Repair: £150-350
- Greenstar 8000 Life System Repair: £150-350
- Greenstar 8000 Life/Style Repair: £180-450
- Greenstar 8000 Style Repair: £150-300
Source
Worcester Bosch 306 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