BoilerFaultCodesWorcester Bosch 203 Fault Code
The Worcester Bosch 203 fault code means: your boiler is currently sitting in standby mode because it has reached its target temperature and is waiting for a new request for heating or hot water.. It appears on 24 Worcester Bosch models in our database.
Technical description: The boiler is on standby
What causes the Worcester Bosch 203 fault?
This status occurs when the boiler has successfully heated your radiators or water cylinder to the required temperature and no longer needs to fire the burner. It acts as a pause state, where the system monitors for a drop in temperature or a new signal from your thermostat before restarting. There is physically nothing wrong with the appliance; it is simply waiting for the next instruction to provide heat.
DIY fix possible
Check if your room thermostat or programmer is set to a temperature higher than the current room temperature.Ensure the heating and hot water schedules are set to 'On' or 'Auto'.Wait a few minutes to see if the boiler fires up once the system temperature drops slightly.
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 203 fault code
Click a model for the full fault code list and model-specific repair notes.
- 1000
- 24 RSF
- 26 CDi Xtra
- 30i Junior Repair: £0-50
- 35 RSF
- Danesmoor
- GB162
- Greenstar 12i System
- Greenstar 2000
- Greenstar 27CDi
- Greenstar 28CDi
- Greenstar 4000
- Greenstar 8000
- Greenstar 8000 Life
- Greenstar 8000 Life System
- Greenstar 8000 Life/Style
- Greenstar 8000 Style
- Greenstar CDi Compact
- Greenstar Heatslave II
- Greenstar i
- Heatslave
- Hideaway
- Junior 24i
- Junior 28i
Source
Worcester Bosch 203 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