Complete guide to Greenstar, CDi, Si, Ri, Life series fault codes with troubleshooting advice
Worcester Bosch boilers display fault codes on the digital screen when something needs attention. Use our comprehensive guide below to identify your error code.
Tip: Worcester codes are typically letters and numbers (e.g., EA, E9, H07, C6). Note down the exact code shown on your display.
| Code | Meaning | Quick Fix | DIY? |
|---|---|---|---|
| EA | Ignition failure - boiler failed to light after multiple attempts | Check gas supply is on, thaw frozen condensate pipe in winter, reset boiler | Partial |
| A1 | Burner not shutting down correctly - flame still detected | Do NOT reset repeatedly - call Gas Safe engineer immediately | No |
| A2 | Burner lit while gas valve closed | Turn off boiler immediately - call engineer urgently | No |
| E2 | Flame loss during operation | Check gas supply, thaw condensate pipe if frozen, reset | Partial |
| E3 | False flame detection | Do NOT reset repeatedly - call engineer | No |
| E7 | Flame signal failure during operation | Check gas supply, reset boiler | Partial |
| Code | Meaning | Quick Fix | DIY? |
|---|---|---|---|
| H07 | Low water pressure - below safe operating level | Top up pressure using filling loop to 1.0-1.5 bar, reset boiler | Yes |
| CE | Water pressure too high - above safe limit | Bleed a radiator to release excess pressure | Partial |
| 2E | Flow rate too low | Check for airlocks, bleed radiators | Partial |
| 2P | Circulation fault - inadequate water flow | Check radiators are on, bleed system, check pump | Partial |
| H06 | Pressure sensor fault | Reset boiler | No |
| H08 | No pressure change when heating | Check system has adequate water, reset | No |
| Code | Meaning | Quick Fix | DIY? |
|---|---|---|---|
| E9 | Overheat protection activated - boiler too hot | Let boiler cool, check radiators are on and TRVs open, bleed air from system | Partial |
| D1 | Flow NTC thermistor fault | Reset boiler | No |
| D2 | Return NTC thermistor fault | Reset boiler | No |
| D3 | Flow NTC temperature too high | Let boiler cool, check circulation | Partial |
| D4 | Temperature rise too fast | Check circulation, bleed radiators | Partial |
| D5 | DHW NTC sensor fault - hot water temperature issue | Reset boiler | No |
| D6 | Return temperature higher than flow | Check system circulation | No |
| Code | Meaning | Quick Fix | DIY? |
|---|---|---|---|
| C6 | Fan speed fault - not reaching required RPM | Reset boiler, check flue terminal is clear of debris | No |
| C1 | Air pressure switch fault | Reset boiler, check flue is not blocked | No |
| C2 | Air pressure switch stuck closed | Reset boiler | No |
| C3 | Condensate pump fault | Check condensate pipe is not blocked or frozen | Partial |
| C4 | Fan not running when expected | Reset boiler | No |
| C5 | Fan running when not expected | Reset boiler | No |
| C7 | Fan speed below minimum | Reset boiler, check flue | No |
| Code | Meaning | Quick Fix | DIY? |
|---|---|---|---|
| B1 | Coding plug not detected | Reset boiler | No |
| B2 | Coding plug fault | Reset boiler | No |
| B3 | Gas type setting incorrect | Reset boiler | No |
| B4 | PCB memory fault | Reset boiler | No |
| E1 | PCB fault - general electronics error | Reset boiler | No |
| E5 | External sensor fault | Check sensor wiring, reset | No |
| E6 | Internal sensor fault | Reset boiler | No |
Most Worcester Bosch boilers can be reset by pressing and holding the reset button:
Important: If the boiler locks out again immediately after resetting, do NOT keep resetting. This can damage components. Call a Gas Safe engineer.
Our Gas Safe engineers service all Worcester Bosch models across Harrow and London.