Worcester Bosch Fault Codes
Comprehensive reference table of all Worcester Bosch boiler error codes. Click any code for detailed troubleshooting steps.
Pro Tip
Check your boiler's digital display panel (usually behind a drop-down cover) to find the current active fault code.
| Error Code | Description | Applies To |
|---|---|---|
| EA 227 | No flame detected; ignition failure or lack of ionisation. | Greenstar i / CDi |
| EA 229 | Loss of flame signal during active operation; flame extinguished. | Greenstar i / CDi |
| 227 V | No flame signal after ignition; burner control unit may require replacement. | Greenstar 4000 / 8000 |
| 228 V | Flame signal detected without a physical flame present; air/gas valve fault. | Greenstar 4000 / 8000 |
| E9 219 | Safety sensor fault; flow temperature too high, sensor open/short circuit. | Greenstar i / Si Compact |
| E9 224 | Flue gas thermostat or maximum safety limit thermostat activated. | Greenstar i / CDi |
| E9 276 | Primary flow temperature has exceeded 95°C; potential pump failure. | Greenstar i / CDi |
| A1 281 | Pump is stuck, blocked, or running with air in the system. | Greenstar i / CDi |
| C6 215 | Fan speed too high; check the fan harness and tachometer connector. | Greenstar Si Compact |
| C7 214 | Fan not running during the start-up phase; electrical or mechanical failure. | Greenstar Si Compact |
| C7 216 | Fan speed too low; check fan wiring harness. | Greenstar i / CDi |
| C1 264 | Airflow stopped entirely during active appliance operation. | Greenstar i / CDi |
| C4 273 | Continuous fan operation detected for the last 24 hours; appliance blocked. | Greenstar i / CDi |
| D1 240 | Return sensor error; sensor may be wet, damaged, or short-circuited. | Greenstar CDi Compact |
| E2 222 | Central heating flow NTC sensor short-circuited or defective. | Greenstar i / CDi |
| FA 306 | False flame fault; ionisation detected after the gas valve has closed. | Greenstar i / Si |
| F7 228 | Ionisation current detected before the burner has started. | Greenstar i / CDi |
| 9U 233 | Heat Control Module (HCM) or control box is defective, loose, or unplugged. | Greenstar Si Compact |
| 9A 362 | Incorrect Heat Control Module (HCM) fitted to the boiler mainboard. | Greenstar Si Compact |
| 360 V | Incompatible code plug detected; check installation of the specific code plug. | Greenstar 8000 Life |
| FD 231 | Mains power fault; electrical power interrupted during a lockout state. | Greenstar CDi Regular |
| F0 238 | Gas valve or control box error; the gas valve internal coils require checking. | Greenstar i / CDi |
| B7 257 | Internal control board problem or potential defect in the HCM. | Greenstar i / CDi |
| D4 341 | Primary flow temperature is rising too fast; check system circulation. | Greenstar i / CDi |
| 1017 W | System water pressure is too low; requires manual re-pressurisation. | Greenstar 8000 Style |
| 1021 B | Hot water temperature sensor is defective or the plug is disconnected. | Greenstar 8000 Style |
| 1037 W | Outside temperature sensor is defective; check the connecting lead. | Greenstar 8000 Style |
| 1065 B | Internal pressure sensor is faulty, blocked with sludge, or not connected. | Greenstar 8000 Style |
| 2927 B | Flame failed during burner operation; check gas line and ionisation electrode. | Greenstar 8000 Style |
| 815 W/B | Low loss header temperature sensor faulty or installed incorrectly. | Greenstar 8000 Style |
| A5 | Internal tank negative temperature coefficient (NTC) thermistor defect. | CDi Highflow |
| D5 | Condensate pump failure; unable to discharge accumulated acidic water. | CDi Highflow |
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