Do you have a Worcester Bosch boiler error code problem?
Where do you keep your Worcester Bosch boiler manual? If finding it involves spending time rummaging through drawers, we can save you the trouble. Below, we’ve pulled together a list of (almost) all of the error codes that Worcester Bosch boilers might display, along with some handy tips on just what each code is trying to tell you.
If your Worcester Bosch boiler’s on the blink, read on to help diagnose the fault.
A quick word of warning before you do: unless you are a qualified heating engineer, do not remove the boiler case, unscrew any panels or remove any parts. Only Gas Safe engineers are allowed to do these things, and for good reason.
If you don’t see your boiler model below, or you see it but simply don’t know what to do with the knowledge that it’s your hot water negative thermistor coefficient sensor that’s playing up, don’t despair. You can book a 15-minute video call with an experienced professional through Herofix, to help you diagnose the fault.
Worcester Bosch boilers we have covered in this error code list:
- CDI Classic Combi Boiler Error Codes
- CDI Classic Regular Boiler Error Codes
- CDI Highflow Combi Boiler Error Codes
- GB162 Boiler Error Codes
- Greenstar 8000 Boiler Error Codes
- Greenstar i System / Combi Boiler Error Codes
- Greenstar Ri Boiler Error Codes
Worcester Bosch CDI Classic Combi Boiler Error Codes
| Error | System Behaviour |
|---|---|
| A1 | Water is leaking or the pump needs replacing or freeing due to the pump running dry. |
| A7 | The hot water negative thermistor coefficient (NTC) sensor is defective – the hot water sensor or connecting leads need checking. |
| A8 | Break communication to FX sensor controls electrical connections need checking. |
| B1 | Code plug not detected. |
| C6 | Fan speed too low – the fan lead and connector need checking and may need replacing. |
| E2 | Central heating (CH) water flow negative thermistor coefficient (NTC) sensor defective check CH flow NTC sensor and connection leads |
| E9 | Safety temperature limiter in central heating (CH) flow has tripped the system pressure or safety temperature limiter needs checking |
| EA | Flame not detected due to a gas issue – the gas supply, power supply or igniter, electrode and lead need checking – contact a Gas Safe installer. |
| F0 | Internal error – electrical connector contacts or programmer interface module – check ignition leads are not loose. |
| F7 | Flame detected even though the appliance is switched off – check the electrode assembly is dry and the pcb and flue are clear. |
| FA | Flame detected after gas shut off – the gas valve needs checking – hire a Gas Safe installer. |
| FD | Reset button pressed by mistake – press reset button again. |
Worcester Bosch CDi Classic Regular Boiler Error Codes
| Error | System Behaviour |
|---|---|
| B1 | Code plug not detected |
| C6 | Fan speed to low |
| E2 | Central heating (CH) flow negative thermistor coefficient (NTC) sensor defective |
| E9 | Safety temperature limiter in central heating (CH) flow has tripped |
| EA | Flame not detected |
| F0 | Internal Error |
| F7 | Flame detected even though appliance switched off |
| FA | Flame detected after gas shut off |
| FD | The reset button pressed by mistake |
Worcester Bosch CDI Highflow Combi Boiler Error Codes
| Error | System Behaviour |
|---|---|
| A1 | Pump dry run detection or pump is running in air the system pressure needs checking |
| A5 | Tank negative thermistor coefficient (NTC) defect |
| A7 | Domestic hot water (DHW) negative thermistor coefficient (NTC) defect |
| A8 | Energy Management System (EMS) communication error |
| B1 | Code plug not detected |
| B2, B3, B4, B5, B6 | Data error |
| B7 | Burner control error |
| C6 | Fan defect |
| D3 | External temperature limiter |
| D5 | Condensate pump failure |
| D6 | Internal heat bank overflow |
| EA | Flame not detected |
| E2 | Primary negative thermistor coefficient (NTC) defect |
| E9 | Safety temperature limiter in central heating (CH) flow stat tripped |
| F0 | Internal error |
| F1 | ROM fault |
| F7 | Flame detected after appliance has been shut off |
| FA | Flame detected after gas shut off |
| FD | Reset button pressed – try pressing the reset button again |
Worcester Bosch CDI Highflow Combi Boiler Error Codes (Continued)
| Error | System Behaviour |
|---|---|
| Light off | No boiler demand |
| Light on | Heating demand on boiler is OK |
| 1 flash 5 seconds off | No ionisation detected after ignition |
| 2 flashes 5 seconds off | Loss of ionisation signal during operation |
| 3 flashes 5 seconds off | Gas valve error |
| 4 flashes 5 seconds off | First safety timing error / ignition timing error |
| 5 flashes 5 seconds off | Ionisation detected after burner stopped |
| 5 flashes 5 seconds off | Gas valve EV2 leak test failed |
| 5 flashes 5 seconds off | Gas valve EV1 leak test failed |
| 5 flashes 5 seconds off | Ionisation current detected before burner start |
| 5 flashes 5 seconds off | Gas valve error |
| 5 flashes 5 seconds off | Ionisation sensor shorted |
| 4 flashes 5 second gap 1 long flash | Sensor test failed |
| 4 flashes, 5 second gap, 2 long flashes | Safety temperature too high |
| 4 flashes, 5 second gap, 3 long flashes | Max safety thermostat activated |
| 4 flashes, 5 second gap, 4 long flashes | Return temperature too high |
| 4 flashes, 5 second gap, 5 long flashes | Flow temperature too high – supply sensor exceeded 110°c |
| 1 long flash, 4 quick flashes, 5 second gap, 1 long flash, 4 quick flashes | Heating control module (HCM) defective |
| 2 long flashes, 4 quick flashes, 5 second gap, 2 long flashes, 4 quick flashes | Fan running too fast |
| 2 long flashes, 4 quick flashes, 5 second gap, 2 long flashes, 4 quick flashes | Fan running too slow |
| 2 long flashes, 4 quick flashes, 5 second gap, 2 long flashes, 4 quick flashes | No airflow after defined period of time |
| 2 long flashes, 4 quick flashes, 5 second gap, 2 long flashes, 4 quick flashes | Fan not running |
| 3 long flashes, 4 quick flashes, 5 second gap, 3 long flashes, 4 quick flashes | Mains voltage interrupted after locking error |
| 4 long flashes, 4 quick flashes, 5 second gap, 4 long flash, 4 quick flashes | Internal control board faults |
| 5 long flashes, 4 quick flashes, 5 second gap, 5 long flash, 4 quick flashes | All other miscellaneous faults – reset the boiler by turning the control knob anti-clockwise to the reset position |
Worcester Bosch Error Code EA 229 or D5
If you’re seeing the error code EA 229 or D5 on your Worcester Bosch boiler, this means that the condensate pipe is frozen. This happens due to the condensate pipe running outside and is an issue that you could fix yourself, if you feel confident enough. You can find out how in our handy guide.
Worcester Bosch GB162 Boiler Error Codes
| Error | System Behaviour |
|---|---|
| 208 | The boiler is in chimney sweep mode |
| 200 | The boiler is in heating mode |
| 201 | The boiler is in domestic hot water (DHW) mode |
| 202 | The boiler is waiting – there was a heat demand from the on off or modulating control |
| 203 | The boiler is on standby |
| 204 | The boiler is waiting – the actual temperature is higher than the calculated or selected boiler temperature |
| 212 | The temperature recorded by the flow temperature sensor or the safety sensor is rising too quickly |
| 226 | Diagnosis tool was connected and is now locked out |
| 260 | The flow temperature sensor is not detecting a rise in temperature following a burner start |
| 265 | The boiler is waiting in response to a heat demand – the boiler regularly switches to partial load |
| 268 | Component test phase |
| 270 | The boiler is modulating upwards |
| 283 | The boiler is preparing for a burner start – the fan and pump are activated |
| 284 | The gas valve is switched |
| 305 | The boiler is waiting for domestic hot water (DHW) operation to end |
| 235 | The KIM (boiler identification module) is too new for the burner control unit |
| 360 | The KIM that has been fitted is not compatible with the burner control unit |
| 9A 361 | The burner control unit that has been fitted is not compatible with the KIM (boiler identification module) |
| 9U 233 | The burner control unit or KIM (boiler identification module) is faulty |
| A3 317 | Short circuit in the flue gas temperature sensor contacts |
| B7 257 | The burner control unit or the KIM (boiler identification module) is faulty |
| C1 264 | No control signal or power supply to the fan during operation |
| C4 273 | The boiler was switched off for a maximum of 2 minutes because it had been operating continuously for more than 24 hours |
| C6 215 | The fan speed is too high |
| C6 216 | The fan speed is too low |
| C7 214 | The fan does not run during the start phase |
| C7 217 | The fan speed is irregular when starting up |
| CE 207 | Water pressure is too low |
| CE 266 | Pump test failed |
| D1 240 | The contacts of the boiler return temperature sensor have been short-circuited |
| D1 241 | The contacts of the boiler return temperature sensor have been interrupted |
| D3 232 | The external switching contact has opened |
| D4 213 | The actual temperature recorded by the flow temperature sensor or return temperature sensor is rising too quickly |
| D4 271 | Actual temperature differential between flow and safety temperature sensor is too high |
| D4 286 | The boiler return temperature sensor has detected a return temperature higher than 105°c |
| E2 222 | Short circuit in the flow temperature sensor contacts |
| E2 223 | The flow temperature sensor contacts have been interrupted |
| E5 218 | The temperature captured by the flow temperature sensor exceeded 105°c |
| E9 210 | The temperature measured by the flue gas sensor is too high and is open |
| E9 219 | The safety temperature sensor has captured a temperature in excess of 105°C |
| E9 220 | The contacts for the safety temperature sensor have shorted or the safety temperature sensor has detected a temperature higher than 130°c |
| E9 224 | The contacts of the safety temperature sensor have been interrupted |
| E9 276 | The temperature flow sensor has measured a temperature in excess of 95°c |
| E9 277 | The safety temperature sensor has measured temperature in excess of 95°c |
| E9 285 | The boiler return temperature sensor has measured a temperature higher than 95°c |
| E9 318 | The flue gas temperature sensor contacts have been interrupted |
| EA 227 | An insufficient ionisation current was measured following ignition of the burner |
| EA 229 | The ionisation current detected by the system during the burning phase was insufficient |
| EA 234 | The contacts of the gas valve have been interrupted |
| EA 261 | The burner control unit is faulty |
| EA 269 | The ignition device has been activated for too long |
| F0 238 | The burner control unit KIM (boiler identification module) is faulty |
| F0 239 | The burner control unit KIM (boiler identification module) has an error. Cabling might have poor contact breaks and pinching or the plug and wiring of the burner control unit needs checking, also check the operating characteristics of the boiler by replacing the burner control unit. |
| F0 242, F0 243. F0 244. F0 245, F0 246. F0 247, F0 248, F0 249, F0 250, F0 251, F0 252, F0 253, F0 255, F0 259, F0 263, F0 267, F0 272 | The burner control unit (KIM) is faulty – the wiring of the burner control unit needs checking, also check the operating characteristics of the boiler by replacing the burner control unit. |
| F0 278 | The sensor test has failed – cabling and plug sensors need checking |
| F0 279 | The burner control unit, or KIM, is faulty – control unit may need replacing |
| F0 280 | The burner control unit is faulty |
| F0 287 | The burner control unit, or KIM, has an error |
| F0 290 | The burner control unit, or KIM, is faulty |
| F7 228 | An ionisation current was measured before the burner started |
| F7 328 | A brief power failure has occurred |
| FA 306 | An ionisation current was measured after the burner went out |
| FD 231 | The mains voltage was interrupted during an interlocking fault |
| EC 256 | The burner control unit has an error |
| EH 258 | The burner control unit is faulty – check the plug and wiring of the burner control unit. |
| H07 | The current water pressure is too low, limiting the performance in heat mode as well as domestic hot water (DHW) mode |
| HrE | The boiler keeps resetting |
| rE | The boiler resets |
Worcester Bosch Greenstar 8000 Boiler Error Codes
| Error | System Behaviour |
|---|---|
| 200 O | Boiler in heating mode |
| 201 O | Boiler in hot water mode |
| 202 O | Boiler in anti-cycle mode |
| 203 0 | Boiler in standby – no heat energy demand |
| 204 O | Current primary water temperature higher than set value |
| 208 0 | Chimney sweep demand |
| 224 V | Safety temperature limiter has tripped – top-up water until the reset pressure is reached |
| 227 V | No flame signal after ignition burner control unit could need replacing |
| 228 V | Flame signal without flame present – air/gas ratio control valve may need replacing as might the ionisation cable |
| 305 0 | Boiler in hot water anti-cycle mode |
| 306 V | Flame signal after closing the fuel supply – the air/gas ratio control valve might need replacing |
| 360 V | Incompatible code plug – check if a correct code plug is installed and exchange or reconnect code plug |
| 815 W/B | Low loss header temperature sensor faulty – check the sensor port or check the differential sensor for incorrect installation position or breakage |
| 1010 O | No BUS communication cable, EMS-Bus isn’t connected or damaged – connect the cable for the EMS-Bus or replace the damaged cable exchange fuse |
| 1017 W | Water pressure too low – the water needs topping up and the vent system or pressure sensor may need replacing |
| 1021 B | Hot water temperature sensor is defective – the plug to the hot water temperature sensor may not be connected |
| 1022 B | Hot water storage temperature sensor is defective – connect the plug to the hot water temperature sensor correctly, mount the hot water temperature sensor correctly or replace the hot water temperature sensor |
| 1037 W | Outside temperature sensor is defective – check the connecting lead |
| 1065 B | Pressure sensor defective or not connected – check pressure sensor connection as it may need replacing |
| 1068 W | Outside temperature sensor defective – check the connecting lead |
| 1073 W | Short circuit of the flow temperature sensor – the temperature sensor may need replacing |
| 1074 W | No signal from the flow temperature sensor available – connect the plug to the flow temperature sensor correctly or temperature sensor could need replacing |
| 1075 W | Short circuit of the temperature sensor at the heating block – temperature sensor may need replacing |
| 1076 W | No signal from the temperature sensor at the heating block available – replace the temperature sensor, the connecting lead or the control unit |
| 2920 V | Error with the flame monitoring |
| 2924 V | No feedback from the modulating gas valve. The gas valve relay is defective – press the reset button and apply burner start, wait to see if fault reoccurs, if it does the gas valve needs replacing |
| 2925 V | Feedback from the modulating gas valve is too low |
| 2927 B | Flame failed during burner operation. Open the main shut off valve, shut down the appliance and check gas line, replace the ionisation electrode, set burner correctly and minimum rated load, check the integrity flue system and if the interconnected room air supply is too small, or the size of the ventilation opening is too small, clean the heating block on the flue gas side or replace the control unit/burner control unit |
| 2946 V | Incorrect code plug detected – the code plug needs replacing |
| 2948 B | No flame signal. With low output the burner starts automatically after cleaning. If the fault occurs repeatedly, the setting of the CO2 valves need checking |
| 2950 B | No flame signal. Following starting procedure the burner starts automatically. After cleaning set the correct gas / air ratio correctly |
| 2963 B | Signal from flow and heat exchanger temperature sensor outside the permissible range – the connecting lead needs connecting correctly |
| 2964 B | Flow rate in heat exchanger is too low |
| 2965 B | Flow temperature too high |
| 2966 B | Flow temperature rise in heat exchanger too rapid |
| 2967 B | Flow / heat exchanger temperature sensor differential too great |
| 2970 B | Pressure drop in heating system too rapid |
| 2971 B | System pressure too low – the heating system needs venting or water needs topping up until the preset pressure is reached. Replace the cable to the pressure sensor replace the pressure sensor |
Worcester Bosch Greenstar I System/Combi Boiler Error Codes
| Error | System Behaviour |
|---|---|
| 226 | Service tool has been connected in the blocking error history menu |
| FD 231 | The power has been interrupted during a lockout |
| C7 214 | Fan does not run during the start up phase – fan harness connector needs checking |
| C6 215 | Fan speed too high – check the fan harness and connector |
| C7 216 | Fan speed too low – check the fan harness and connector |
| C7 217 | Fan has stopped during appliance operation |
| C1 264 | Fan stopped during operation |
| C4 273 | Continuous fan operation for the last 24 hours – appliance temporarily blocked |
| E2 222 | Flow temperature sensor shorted |
| E2 233 | Flow temperature sensor disconnected |
| E9 276 | Primary flow temperature exceeded 95°c |
| E2 350 | Flow temperature sensor shorted |
| E2 351 | Flow temperature sensor disconnected |
| FA 306 | Ionisation detected after the gas valve closed |
| EA 227 | No ionisation detected after ignition |
| F7 228 | Isioniation current detected before burner start |
| EA 229 | Loss of ionisation signal during operation |
| EA 261 | Heat control module (HCM) potentially defective – reset the appliance |
| 9U 233 | Control box or heat control module (HCM) is defective or loose, the HCM needs to be checked |
| C4 237 | Control box or heat control module (HCM) is defective |
| F0 238 | Gas valve or control box error – gas valve coils need checking |
| F0 239 | Control box or the heat control module (HCM) is defective – the control box connections need checking |
| F0 242 | Control box or the heat control module (HCM) is defective – the HCM and control box connections need to be checked |
| B7 257 | Control box or the heat control module HCM) is defective- the HCM and control box connections need to be checked |
| F0 258 | Control box or the heat control module (HCM) is defective – HCM or control box connections need to be checked |
| EH 258 | Control box or the heat control module (HCM) is defective – HCM or control box connections need to be checked |
| F1 259 | Control box or the heat control module (HCM) is defective – HCM or control box connections need to be checked |
| F0 262 | Control box or the heat control module (HCM) is defective – HCM or control box connections need to be checked |
| F1 263 | Control box or the heat control module (HCM) is defective – HCM or control box connections need to be checked |
| F0 272 | Control box or the heat control module (HCM) is defective – control box and connections need checking or HCM might not be inserted properly and need replacing |
| F0 280 | Control box or the heat control module (HCM) is defective – control box and connections need checking or HCM might not be inserted properly and need replacing |
| F0 290 | Control box is defective – HCM needs checking as it might not be inserted properly or need replacing |
| 328 | Internal error with the mains voltage – frequency may be inconsistent |
| 235 | Incompatible heat control module (HCM) software versions – control box needs latest software |
| 356 | Low mains voltage – the voltage may be interrupted or inconsistent and needs checking |
| 360 | Heat control module (HCM) invalid – the inserted HCM does not correspond with the control box |
| A8 362 | Low mains voltage – the voltage may be interrupted, inconsistent or heat control module (HCM) invalid |
| CC 800 | Outdoor sensor defect available when accessory outdoor sensor is connected |
| A1 281 | Pump stock or running dry |
| E9 224 | Flue or high limit thermostat activated |
| D4 341 | Primary flow temperature rising too fast |
Worcester Bosch Greenstar Ri Boiler Error Codes
| Error | System Behaviour |
|---|---|
| Fault Description | System Behaviour |
| No light | No power at control board |
| Light on | Appliance on but not operating during demand |
| Slow flash ( mostly off flashes on) | Ignition lockout |
| Slow flash ( mostly on flashes off) | Flue overheat or heat exchanger overheat |
| Fast flash | Volatile lockout sensor fan or code plug |
| 2 pulses | Check service mode switch is in minimum position |
| 5 pulses | Check service mode switch is in max position |
Still none the wiser? Or feeling that the required repair is beyond your ability to fix? Either way, you can book a 15-minute video call with one of the professionals at Herofix.com for expert advice and guidance on next steps.
