UK & Ireland
Worcester Bosch error codes
Worcester Bosch Greenstar boilers show a fault as a two-character code, such as EA or E9. On Greenstar i and Si boilers a three-digit number appears under it, as in EA 227. The Greenstar 4000 shows a number on its own, such as 1017.
- 13 codes
- Boilers
- Checked against official pages
Boilers 13 codes
EA 227 No flame detected
The boiler couldn't detect a flame, so it has locked out.
1017 System pressure too low
The water pressure in your heating system is too low.
A1 Pump has run dry
The boiler's pump has been running without enough water in the system, so the boiler has locked out.
E9 Overheat: safety limiter tripped
A safety thermostat or temperature limiter has tripped because part of the boiler got too hot, so the boiler has locked out.
C6 Fan speed fault
The boiler's fan isn't turning at the right speed, so the boiler has stopped.
D5 Condensate pump fault
On Worcester's Greenstar FS CDi floor-standing boilers, d5 means a fault with the condensate pump, which pumps the boiler's waste water away.
E2 Heating flow sensor fault
The temperature sensor (NTC) on the heating flow is faulty, so the boiler can't read the water temperature.
F0 Internal error
The boiler's control board has reported an internal error and locked the boiler out.
EA 229 Flame lost while running
The burner lit, but the flame went out while the boiler was running, so it has locked out.
EA 234 Gas valve electrical fault
The boiler has found an electrical problem with its gas valve, such as a coil that's disconnected, so it has locked out.
CE 207 System water pressure too low
The heating system has lost water pressure.
2964 Water flow through the boiler too low
Not enough water is flowing through the boiler's heat exchanger.
A8 Lost contact with the heating controls
The boiler has lost communication with its programmer or room control.
No codes of that type for this brand.
Good to know
- Resetting depends on the model. Greenstar CDi Classic: hold the reset button for 3 seconds. Greenstar i and Si: press the reset button briefly once. Greenstar 4000: hold the up and down arrow keys until Reset shows.
- Some codes can't be cleared by a simple reset. When you call Worcester about a fault, give the code and the three-digit number under it.
- Worcester's general advice on pressure is 1 to 1.5 bar on the gauge when the system is cool. Topping up once or twice a year is normal.
- Before you call anyone, check the gas: do your cooker or hob work, and if you have a prepayment meter, is there credit on it?
- If you smell gas, turn it off at the meter and call the National Gas Emergency Service on 0800 111 999.
Official help pages
- Worcester Bosch Greenstar CDi Classic user instructions (PDF)
- Worcester Bosch: how often should I top up the pressure?
- Worcester Bosch: the heating system is constantly losing pressure
- Worcester Bosch Greenstar 4000 user instructions (PDF)
Every code page links the exact pages it was checked against. Last reviewed October 2026.
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344 codes from 24 brands, each one checked against the maker's own manuals and support pages.