Worcester Bosch Fault Codes
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Worcester Bosch Fault Codes
Boilers covered:
- Greenstar Ri, Greenstar Ri ErP
- Greenstar Ri ErP+
- Greenstar Ri Compact
- Greenstar i Combi
- Greenstar i System
- Greenstar i System ErP
- Greenstar CDi Compact
- Greenstar Si Compact
- Greenstar 2000
- Greenstar 4000 Combi
- Greenstar 4000 System
- Greenstar 8000 Life Combi
- Greenstar 8000 Life System
- Greenstar 8000 Life Regular
- Greenstar 8000 Style Combi
- Greenstar 8000 Style System
- Greenstar 8000+ Combi
- Greenstar 8000+ System
- Greenstar 8000+ Regular
- Greenstar 8000+ Style
- Greenstar 8000 F Combi
- Greenstar 8000 F Regular
- Greenstar 1000
Important: Many codes share a letter group (e.g. EA, E9, C6) but the cause number after it differs by model. Low-pressure codes and some ignition faults (frozen condensate) have limited homeowner checks. Most others require a Gas Safe engineer.
Modern / Greenstar Range (letter codes)
| Error / Cause code | Possible fault / meaning | If ticked try the troubleshooter |
|---|---|---|
| A1 / A1 281 | Pump stuck, dry running, air in system, or low water pressure | ✓ |
| A7 | Domestic hot water NTC sensor defective or wiring fault | ✕ |
| A8 / A8 362 | Heat control module (HCM) invalid / EMS communication fault | ✕ |
| B1 | Code plug not detected or incorrectly fitted | ✕ |
| B7 / B7 257 | Internal error / control board / burner control unit fault | ✓ |
| C1 / C1 264 | Fan stopping during operation / airflow interruption / no control signal to fan | ✕ |
| C4 / C4 273 / C4 237 | Control box / HCM defective, fan failed to stop, or airflow present for 24 hours | ✕ |
| C6 / C6 215 / C6 216 | Fan speed too high or too low | ✕ |
| C7 / C7 214 / C7 216 / C7 217 | Fan not running on start-up or during operation / airflow blocked | ✕ |
| CC / CC 800 | Outdoor temperature sensor defect | ✕ |
| CE 207 | Water pressure too low | ✓ |
| D1 / D1 240 / D1 241 / D1 286 | Return temperature sensor error, short circuit, wet, disconnected, or overheat | ✕ |
| D4 / D4 271 / D4 213 / D4 341 | Primary flow temperature rising too fast / flow-safety sensor difference too high | ✕ |
| D5 | Condensate pump failure | ✕ |
| E2 / E2 222 / E2 223 / E2 233 / E2 350 / E2 351 | Flow temperature sensor fault, short circuit, or disconnected | ✕ |
| E5 / E5 218 / E5 332 | Flow temperature too high / primary flow sensor overheated | ✕ |
| E9 / E9 219 / E9 220 / E9 221 / E9 224 / E9 276 / E9 277 / E9 285 | Safety temperature limiter, overheat, flue thermostat, or max temperature sensor fault | ✕ |
| EA / EA 227 / EA 229 / EA 234 / EA 261 / EA 269 / EA 338 | No flame / ionisation detected after ignition, flame loss, gas valve issues, or too many short starts (often gas, electrode, or condensate) | ✓ |
| EF 349 | Central heating boil detected (flow/return difference >18°C at low load) | ✕ |
| F0 / F0 237 / F0 238 / F0 239 / F0 242 / F0 253 / F0 258 / F0 259 / F0 262 / F0 263 / F0 267 / F0 272 / F0 278 / F0 279 / F0 280 / F0 287 / F0 290 | Internal error, gas valve, control box, or HCM fault | ✓ |
| F1 / F1 259 / F1 263 | Control or related electronics fault (model dependent) | ✕ |
| F7 / F7 228 / F7 328 | False flame / ionisation detected before burner start | ✕ |
| FA / FA 306 / FA 364 | Flame detected after gas shut-off / gas valve EV2 leak test failed | ✕ |
| FB 365 | Gas valve EV1 leak test failed | ✕ |
| FD / FD 231 | Power interrupted or reset button pressed by mistake | ✓ |
Classic / Numeric Codes
| Error / Cause code | Possible fault / meaning | If ticked try the troubleshooter |
|---|---|---|
| 9A 362 / 9A 361 | Incorrect HCM / burner control unit incompatibility | ✕ |
| 9U / 9U 233 | HCM / code plug / burner control unit or KIM error | ✕ |
| 1017 / 1017 W | Low water pressure (newer models) | ✓ |
| 1021 / 1021 B / 1022 / 1022 B | Hot water temperature sensor faults | ✕ |
| 1037 W | Outside temperature sensor defective | ✕ |
| 1065 B / 1070–1076 W | Various sensor or pressure related faults (model specific) | ✕ |
| 1073 / 1074 | Flow temperature sensor short circuit or no signal | ✕ |
| 227 / 227 V | No flame signal after ignition | ✓ |
| 228 / 228 V | Flame signal without flame present | ✕ |
| 229 | Flame failed during burner operation | ✓ |
| 232 | Boiler locked by external switching contact | ✕ |
| 233 / 234 / 235 / 237 / 238 / 242 / 244–254 / 257–263 / 360 / 362 / 363 / 604 | System / electronics / code plug / burner control unit faults (various) | ✕ |
| 281 | Pump stuck or running in air | ✓ |
| 2924 / 2927 B | Gas valve feedback, relay, or flame failure during operation | ✓ |
| 2946 / 2948 | Incorrect or incompatible code plug | ✕ |
| 2964 B / 2965 B / 2971 B | Low flow rate, high flow temperature, or low system pressure | ✕ |
| 200 O / 201 O / 202 O / 203 O / 204 O / 208 O / 305 O | Status codes (heating, hot water, anti-cycle, standby, chimney sweep — not faults) | ✕ |
| T1 / T2 / T3 / T4 / T6 | Test modes (ignition, fan, pump, 3-way valve, ionisation — not faults) | ✕ |
| 815 W/B | Low loss header temperature sensor fault | ✕ |
| 1010 O | No EMS BUS communication | ✕ |