Worcester Bosch Boiler Error & Fault Codes
Your Worcester Bosch boiler is one of the most technical appliances in your home, one that you may take for granted until something goes wrong.
Luckily, boilers are also clever enough to give us a clue to the problem in the form of fault codes. Here we run through them all and what they mean.
Book a boiler repair
What does my Boiler Fault Code mean?
Worcester Bosch boilers can give us with a lot of information through their fault codes, helping professional engineers get a head start when undertaking a repair.
Codes vary between models, with as many as 38 codes helping to provide a picture of what’s gone wrong.
Worcester Bosch Greenstar 30i
Combi Boiler Error Codes
| Fault Codes | Fault |
|
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 Highflow 440 / 550
Combi Boiler Error Codes
| Fault code | Fault |
|
A1 |
Service tool has been connected in the blocking error history menu |
|
A5 |
The power has been interrupted during a lockout |
|
A7 |
Fan does not run during the start up phase – fan harness connector needs checking |
|
A8 |
Fan speed too high – check the fan harness and connector |
|
B1 |
Fan speed too low – check the fan harness and connector |
|
B2, B3, B4, B5, B6 |
Fan has stopped during appliance operation |
|
B7 |
Fan stopped during operation |
|
C6 |
Continuous fan operation for the last 24 hours – appliance temporarily blocked |
|
D3 |
Flow temperature sensor shorted |
|
D5 |
Flow temperature sensor disconnected |
|
D6 |
Primary flow temperature exceeded 95°c |
|
EA |
Flow temperature sensor shorted |
|
E2 |
Flow temperature sensor disconnected |
|
E9 |
Ionisation detected after the gas valve closed |
|
F0 |
No ionisation detected after ignition |
|
F1 |
Isioniation current detected before burner start |
|
F7 |
Loss of ionisation signal during operation |
|
FA |
Heat control module (HCM) potentially defective – reset the appliance |
|
FD |
Control box or heat control module (HCM) is defective or loose, the HCM needs to be checked |
Worcester Bosch Greenstar 8000 life
Combi Boiler Error Codes
| Fault code | Fault |
|
200 O |
Boiler in heating mode |
|
201 O |
Boiler in hot water mode |
|
202 O |
Boiler in anti-cycle mode |
|
203 O |
Boiler in standby – no heat energy demand |
|
204 O |
Current primary water temperature higher than set value |
|
208 O |
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 18Ri / 24Ri
Heat Only Boiler Error Codes
| Fault code | Fault |
|
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 |
Worcester Bosch Boiler Safety Warning
When your Worcester boiler error codes or fault lights flash, don’t do any repair work that involves working with gas as you are required to be Gas Safe Registered by law.
Here at Boiler Plan all our engineers are Gas Safe Registered and will do an amazing job with any Worcester Bosch boiler repair work you may need.
Book a boiler repairProtect your Worcester Bosch Boiler with a Care Plan
There are a whole host of possible faults to be mindful of when it comes to your combi boiler. Which is why it’s best to be protected should anything unforeseen happen to your own heating system.
With our range of affordable care plans, there’ll be no need to fluster should you see a fault code.
Whatever plan you choose, each comes with an annual service to ensure your system is fully maintained and ready to keep your home reliably warm
Choose from:
- Service Plan – Boiler service every year to ensure it’s working correctly
- Gold Package – Includes: 3 call outs per year, annual service, carbon monoxide test.
- Platinum Package – Includes: Unlimited call outs, all parts and labour, repairs to the entire heating system, £500 towards a replacement boiler.
- Boiler Plan Plus Package - For those with a Boiler still in warranty. Includes: Unlimited call outs, all parts and labour, repairs to the rest of your entire heating system.
Cosy up with a better boiler company
We exist to be completely transparent – no bull, no waffle, no confusion.