Worcester broken with an error code? Decode and fix it here.
- Worcester Bosch Fault Codes by Boiler Model
- Worcester Bosch Greenstar i System/Combi Boiler Error Codes
- Worcester Bosch Greenstar Si Compact Error Codes
- Worcester Bosch CDi Classic Regular Boiler
- Worcester Bosch CDi Compact Error Codes
- Worcester Bosch CDi Classic Combi Boiler Error Codes
- Worcester Bosch CDi Highflow Error Codes
- Worcester Bosch 8000 Style Error Codes
If your Worcester Bosch boiler is experiencing an issue it will likely turn off, often termed a ‘lockout’ to prevent further potential damage and ensure you and your home are safe.
At this point, you will usually discover a boiler error code, also called a fault code displayed on the interface. The purpose of this code is to make it easier for you or the engineer to identify the boiler problem and get it repaired quickly.
In this guide, we have put together a comprehensive list of the brand's most common boiler error codes. This should give you an idea of what is wrong with your boiler and potentially how much it may cost to repair.
Please note: You should never attempt to open or tamper with your boiler, any repairs should be done by a qualified Gas Safe Engineer.
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Worcester Bosch Boiler Error Codes
Worcester Bosch has many different error codes which differ by the exact model you own. However, to make things a little easier, the manufacturer has categorised their error codes as follows:
Locking Error
If your boiler has a locking error it will display a flashing fault code accompanied by a triangle. It will also display a static cause code. In order to remove the code, you will need to reset the boiler, however, this should be done after you have repaired the issue.
Blocking Error
The boiler will stop working and power out, but no fault code will be present. In order to access the code, you will need to press the return button. The error will clear once the fault is dealt with.
For example, if the boiler has a blocked condensate pipe, the blockage will need to be cleared and the error will go once the blockage is no longer present.
Fault Error
If your boiler is experiencing a fault, a fault code will be displayed. This will be an alphanumeric fault code.
Maintenance Code
If the code displayed begins with a H, it’s a maintenance code. This fault will not stop the boiler from operating but will need the attention of an engineer.
Cause Error
A three-digit number that is found on your interface when looking for the block code. It can be accessed by pressing the return button when a blocking error occurs. During a locking error, the cause error code should flash intermittently on the screen.
PS You can check out Gas Engineer Allen Hart explaining the most common boiler problems and how you can resolve them in the video below:
Worcester Bosch Fault Codes by Boiler Model
Worcester Bosch Greenstar i System/Combi Boiler Error Codes
The Worcester Bosch Greenstar i was the brand's best-selling combi boiler model, installed in over 1 million UK homes. It was also available as a system boiler and both types use the same error codes.
The Greenstar i is an award-winning boiler and is available in two sizes, the 25i at 25 kilowatts, ideal for small apartments and properties and the 30i at 30 kilowatts, more suitable for the average-sized 3-bedroom home with one bathroom.
The Greenstar i was recently discontinued and replaced by the new and improved Greenstar 4000 model.
Fault Code | Description |
FD | Power interrupted |
C7 | Fan not running on start-up |
C6 | Fan speed too high or too low |
C1 | Fan stopping during operation |
C4 | Fan has failed to stop |
E2 | Flow temperature issue |
E9 | Primary flow temperature exceeding 95° |
FA | Ionisation detected after gas valve closed |
EA | No ionisation detected after ignition |
F7 | Ionisation detected before burner start |
9U | Control box defective or loose |
C4 | Control box or heat control module defective |
F0 | Gas valve/control box error |
A8 | Heat control module invalid |
CC | Outdoor sensor defect |
A7 | |
A1 | Pump stuck or running dry |
E9 | Flue or high limit thermostat activated |
D4 | Primary flow temps rising too fast |
PS Typically a Worcester Bosch error code is accompanied by a blue flashing light.
Worcester Bosch Greenstar Si Compact Error Codes
The Worcester Bosch Greenstar Si boasts very similar credentials to the Greenstar i and is suitable for small and medium-sized properties.
The key difference is the Greenstar Si Compact is designed to fit into smaller more compact spaces such as kitchen cupboards.
Fault code description | |
T1 | Ignition test |
T2 | Fan test |
T3 | Pump test |
T4 | Three way valve test |
T6 | Ionisation oscillator test |
9A 362 error | Incorrect HCM fitted |
9U 233 Heat Control Module (HCM) error | Problem with code plug |
B7 257 Internal error | Potential control board problem |
C6 215 Fan problem | Fan running too fast |
C7 214 Fan problem | Fan not running |
D1 240 Return sensor error | Sensor may be wet or damaged |
E2 222 | Flow sensor short circuit error |
E5 218 | Flow temperature too high |
E9 219 Safety sensor fault | Temperature too high, sensor short circuit or open circuit |
EA 227 | No flame detected or flame signal loss during operation |
F0 237 | Internal error |
F7 228 Flame error | False flame or flame detected before burner started |
FA 306 False flame fault | Flame detected after burner stop |
FD 231 Mains power fault | Electrical power interruption |
FA 364 Gas valve EV2 leak test failed | Gas valve leak |
FB 365 | Gas valve EV1 leak test failed |
A1 281 | Pump stuck or running with air in the system |
C1 264 | Airflow stopped during operation |
C4 273 | Airflow present during last 24 hour |
D4 271 | Temperature difference between flow and safety sensor exceeds limit |
D1 240 | Return sensor short circuit |
E9 224 Max thermostat activated | Flue gas thermostat overheat |
EA 227 | No ionisation detected after ignition |
EF 349 Central heating boil detected | Boiler operating at minimum burner load with temperature difference greater than 18°C between Flow & Return |
NO CODE 212 | Safety or flow temperature rising too fast |
Worcester Bosch CDi Classic Regular Boiler
The Worcester Bosch CDi Classic boiler range is no longer available and has since been replaced by the super sleek Worcester Bosch Greenstar 8000 Style boiler range.
The CDi Classic came in a range of different power outputs including 29kW, 34kW, 38kW and 42kW and was available as a combi boiler or a regular or heat-only model.
These wide-ranging choices made the range suitable for average-sized homes, as well as large homes with above-average hot water demands.
Fault code description | |
B1 | Code plug not detected |
C6 | Fan speed to low or too high |
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 | Reset button pressed by mistake |
Worcester Bosch CDi Compact Error Codes
The Worcester CDi Compact is another one of the brand's popular combi boilers available with power outputs of 28kW, 32kW and 34kW making it ideal for small to average-sized properties.
As the name implies, this boiler has a compact design and is able to fit into a standard-sized kitchen cupboard, making it perfect for those looking for a boiler they can keep hidden away.
Fault code description | |
T1 | Ignition test |
T2 | Fan test |
T3 | Pump test |
T4 | Three-way valve test |
T6 | Ionisation oscillator test |
9A 362 error | Incorrect HCM fitted |
9U 233 Heat Control Module (HCM) error | Problem with code plug |
B7 257 Internal error | Potential control board problem |
C6 215 Fan problem | Fan running too fast |
C7 214 Fan problem | Fan not running |
D1 240 Return sensor error | Sensor may be wet or damaged |
E2 222 | Flow sensor short circuit error |
E5 218 | Flow temperature too high |
E9 219 Safety sensor fault | Temperature too high, sensor short circuit or open circuit |
EA 227 | No flame detected or flame signal loss during operation |
F0 237 | Internal error |
F7 228 Flame error | False flame or flame detected before burner started |
FA 306 False flame fault | Flame detected after burner stop |
FD 231 Mains power fault | Electrical power interruption |
FA 364 Gas valve EV2 leak test failed | Gas valve leak |
FB 365 | Gas valve EV1 leak test failed |
A1 281 | Pump stuck or running with air in the system |
C1 264 | Airflow stopped during operation |
C4 273 | Airflow present during last 24 hour |
D4 271 | Temperature difference between flow and safety sensor exceeds limit |
D1 240 | Return sensor short circuit |
E9 224 Max thermostat activated | Flue gas thermostat overheat |
EA 227 | No ionisation detected after ignition |
EF 349 Central heating boil detected | Boiler operating at minimum burner load with temperature difference greater than 18°C between Flow & Return |
NO CODE 212 | Safety or flow temperature rising too fast |
Worcester Bosch CDi Classic Combi Boiler Error Codes
Launched in 2012, the Worcester Bosch CDi Classic combination boiler was the brand's premium-range model but has since been replaced by the Worcester Bosch 8000.
The CDi Classic was the brand's most powerful combi boiler, available in a range of different power outputs including 29kW, 34kW, 38kW and 42kW, making it suitable for homes with a high hot water demand.
Fault code description | |
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 |
FO | 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 |
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Worcester Bosch CDi Highflow Error Codes
The Worcester Bosch CDi Highflow is a sturdy floor-standing combi boiler with industry-leading hot water flow rates.
The CDi Highflow is ideal for large homes with multiple bathrooms that don’t want to make way for an additional water tank.
It's the best combi boiler for large homes, not many can match its credentials. The best bit? It can be fitted underneath your kitchen counter.
Fault code description | |
A1 | Pump dry run detection or pump is running in the 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 8000 Style Error Codes
The Worcester Bosch 8000 Life is one of the manufacturer’s latest models in the Greenstar range and is considered their premium offering.
Officially recognised as the brand's most powerful boiler model, it is available in power outputs ranging from 30kW all the way up to 45kW, making it the perfect boiler for large-size homes and/or those with high hot water demand.
Read our Worcester Bosch vs Viessmann Boilers review if you need some help in choosing between these two popular brands.
The boiler's exterior is also a game changer, offering homeowners not only a boiler that works great but one that looks great, quite easily the first wall-hung boiler that has a truly impressive aesthetic (available in both black and white).
It’s the perfect solution for those wanting an award-winning, industry-leading boiler with all of the latest and greatest features.
Related reading:
Fault code description | |
200 O | Boiler in heating mode |
201 O | Fan not running on start-up |
202 O | Boiler in anti-cycle mode |
203 O | Boiler in standby mode |
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 O | 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 |
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 |
Related boiler troubleshooting guides:
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