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Worcester Bosch Boiler Error Codes

Worcester Bosch error codes vary depending on the exact model you own. To make things easier, the manufacturer has classified their error codes as follows:.

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.

Ignute my boiler engineer showing woman worcester bosch error codes
Error CodePossible Fault
EA338A leak somewhere, either within your boiler or around the system.
A281A leak somewhere, either within your boiler or around the system.
A41Boiler making loud noises – likely due to a faulty pump or heat exchanger.
EA227Boiler has locked out. This will be to prevent any further damage occurring and to remove potential danger.
E5218Boiler has overheated.
E5332Boiler has overheated.
E9219Boiler has overheated.
E9224Boiler has overheated.
D1286Boiler has overheated.
EA225Condensate pipe is blocked.
D5Condensate pipe is blocked.
U9The boiler flow temperature is too high, which means it will shut down until it has cooled down.
Error CodePossible Fault
A1Water is leaking or the pump needs replacing or freeing due to the pump running dry.
A7The hot water negative thermistor coefficient (NTC) sensor is defective – the hot water sensor or connecting leads need checking.
A8Break communication to FX sensor controls electrical connections need checking.
B1Code plug not detected.
C6Fan speed too low – the fan lead and connector need checking and may need replacing.
E2Central heating (CH) water flow negative thermistor coefficient (NTC) sensor defective check CH flow NTC sensor and connection leads.
E9Safety temperature limiter in central heating (CH) flow has tripped the system pressure or safety temperature limiter needs checking.
EAFlame not detected due to a gas issue – the gas supply, power supply or igniter, electrode and lead need checking – contact a Gas Safe installer.
F0Internal error – electrical connector contacts or programmer interface module – check ignition leads are not loose.
F7Flame detected even though the appliance is switched off – check the electrode assembly is dry and the pcb and flue are clear.
FAFlame detected after gas shut off – the gas valve needs checking – hire a Gas Safe installer.
FDReset button pressed by mistake – press reset button again.
Error CodePossible Fault
A1Pump dry run detection or pump is running in air the system pressure needs checking
A5Tank negative thermistor coefficient (NTC) defect
A7Domestic hot water (DHW) negative thermistor coefficient (NTC) defect
A8Energy Management System (EMS) communication error
B1Code plug not detected
B2, B3, B4, B5, B6Data error
B7Burner control error
C6Fan defect
D3External temperature limiter
D5Condensate pump failure
D6Internal heat bank overflow
EAFlame not detected
E2Primary negative thermistor coefficient (NTC) defect
E9Safety temperature limiter in central heating (CH) flow stat tripped
F0Internal error
F1ROM fault
F7Flame detected after appliance has been shut off
FAFlame detected after gas shut off
FDReset button pressed – try pressing the reset button again
Error CodePossible Fault
T1Ignition test – checking the igniter spark
T2Fan test – checking the basic fan
T3Pump test – checking the basic pump
T4Three way valve test communication fault
T6Ionisation oscillator test
9A 362Error – incorrect HCM fitted
9U 233Heat Control Module (HCM) error – problem with code plug
B7 257Internal error – possible control board problem
C6 215Fan problem – fan running too fast
C7 214Fan problem – fan not running
D1 240Return sensor error – sensor may be wet or damaged
E2 222Flow sensor short circuit error
E5 218Flow temperature too high
E9 219Safety sensor fault – temperature too high, sensor short circuit or open circuit
EA 227No flame detected or flame signal loss during operation
F0 237Internal error
F7 228Flame error – false flame or flame detected before burner started
FA 306False flame fault – flame detected after burner stop
FD 231Mains power fault – electrical power interruption
FA 364Gas valve EV2 leak test failed – gas valve leak
FB 365Gas valve EV1 leak test failed
A1 281Pump stuck or running with air in the system
C1 264Airflow stopped during operation
C4 273Airflow present during last 24 hour
D1 240Return sensor short circuit
D4 271Temperature difference between flow and safety sensor exceeds limit
E9 224Max thermostat activated – flue gas thermostat overheat
EA 227No ionisation detected after ignition
EF 349Central heating boil detected – boiler operating at minimum burner load with temperature difference greater than 18°C between Flow & Return
NO CODE 212Safety or flow temperature rising too fast
Error CodePossible Fault
B1Code plug not detected
C6Fan speed too low
E2Central heating (CH) flow negative thermistor coefficient (NTC) sensor defective
E9Safety temperature limiter in central heating (CH) flow has tripped
EAFlame not detected
F0Internal error
F7Flame detected even though appliance switched off
FAFlame detected after gas shut off
FDReset button pressed by mistake
Error CodePossible Fault
226Service tool has been connected in the blocking error history menu
FD 231The power has been interrupted during a lockout
C7 214Fan does not run during the start up phase – fan harness connector needs checking
C6 215Fan speed too high – check the fan harness and connector
C7 216Fan speed too low – check the fan harness and connector
C7 217Fan has stopped during appliance operation
C1 264Fan stopped during operation
C4 273Continuous fan operation for the last 24 hours – appliance temporarily blocked
E2 222Flow temperature sensor shorted
E2 233Flow temperature sensor disconnected
E9 276Primary flow temperature exceeded 95°c
E2 350Flow temperature sensor shorted
E2 351Flow temperature sensor disconnected
FA 306Ionisation detected after the gas valve closed
EA 227No ionisation detected after ignition
F7 228Isioniation current detected before burner start
EA 229Loss of ionisation signal during operation
EA 261Heat control module (HCM) potentially defective – reset the appliance
9U 233Control box or heat control module (HCM) is defective or loose, the HCM needs to be checked
C4 237Control box or heat control module (HCM) is defective
F0 238Gas valve or control box error – gas valve coils need checking
F0 239Control box or the heat control module (HCM) is defective – the control box connections need checking
F0 242Control box or the heat control module (HCM) is defective – the HCM and control box connections need to be checked
B7 257Control box or the heat control module HCM) is defective- the HCM and control box connections need to be checked
F0 258Control box or the heat control module (HCM) is defective – HCM or control box connections need to be checked
EH 258Control box or the heat control module (HCM) is defective – HCM or control box connections need to be checked
F1 259Control box or the heat control module (HCM) is defective – HCM or control box connections need to be checked
F0 262Control box or the heat control module (HCM) is defective – HCM or control box connections need to be checked
F1 263Control box or the heat control module (HCM) is defective – HCM or control box connections need to be checked
F0 272Control 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 280Control 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 290Control box is defective – HCM needs checking as it might not be inserted properly or need replacing
328Internal error with the mains voltage – frequency may be inconsistent
235Incompatible heat control module (HCM) software versions – control box needs latest software
356Low mains voltage – the voltage may be interrupted or inconsistent and needs checking
360Heat control module (HCM) invalid – the inserted HCM does not correspond with the control box
A8 362Low mains voltage – the voltage may be interrupted, inconsistent or heat control module (HCM) invalid
CC 800Outdoor sensor defect available when accessory outdoor sensor is connected
A1 281Pump stock or running dry
E9 224Flue or high limit thermostat activated
D4 341Primary flow temperature rising too fast
Error CodePossible Fault
No lightNo power at control board
Light onAppliance 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 flashVolatile lockout sensor fan or code plug
2 pulsesCheck service mode switch is in minimum position
5 pulsesCheck service mode switch is in max position
Error CodePossible Fault
200 OBoiler in heating mode
201 OBoiler in hot water mode
202 OBoiler in anti-cycle mode
203 OBoiler in standby – no heat energy demand
204 OCurrent primary water temperature higher than set value
208 OChimney sweep demand
224 VSafety temperature limiter has tripped – top-up water until the reset pressure is reached
227 VNo flame signal after ignition burner control unit could need replacing
228 VFlame signal without flame present – air/gas ratio control valve may need replacing as might the ionisation cable
305 OBoiler in hot water anti-cycle mode
306 VFlame signal after closing the fuel supply – the air/gas ratio control valve might need replacing
360 VIncompatible code plug – check if a correct code plug is installed and exchange or reconnect code plug
815 W/BLow loss header temperature sensor faulty – check the sensor port or check the differential sensor for incorrect installation position or breakage
1010 ONo 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 WWater pressure too low – the water needs topping up and the vent system or pressure sensor may need replacing
1021 BHot water temperature sensor is defective – the plug to the hot water temperature sensor may not be connected
1022 BHot 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 WOutside temperature sensor is defective – check the connecting lead
1065 BPressure sensor defective or not connected – check pressure sensor connection as it may need replacing
1068 WOutside temperature sensor defective – check the connecting lead
1073 WShort circuit of the flow temperature sensor – the temperature sensor may need replacing
1074 WNo signal from the flow temperature sensor available – connect the plug to the flow temperature sensor correctly or temperature sensor could need replacing
1075 WShort circuit of the temperature sensor at the heating block – temperature sensor may need replacing
1076 WNo signal from the temperature sensor at the heating block available – replace the temperature sensor, the connecting lead or the control unit
2920 VError with the flame monitoring
2924 VNo 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 VFeedback from the modulating gas valve is too low
2927 BFlame 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 VIncorrect code plug detected – the code plug needs replacing
2948 BNo 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 BNo flame signal. Following starting procedure the burner starts automatically. After cleaning set the correct gas / air ratio correctly
2963 BSignal from flow and heat exchanger temperature sensor outside the permissible range – the connecting lead needs connecting correctly
2964 BFlow rate in heat exchanger is too low
2965 BFlow temperature too high
2966 BFlow temperature rise in heat exchanger too rapid
2967 BFlow / heat exchanger temperature sensor differential too great
2970 BPressure drop in heating system too rapid
2971 BSystem 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
Error CodePossible Fault
EA 229 or D5You are experiencing a frozen condensate pipe. This is usually an issue you can fix yourself with some warm (not boiling) water poured over your condensate pipe wherever it has frozen.
Error CodePossible Fault
1021Cylinder charging or hot water temperature sensor faulty.

Turn the appliance off and back on again. The hot water sensor has been changed if an open or short circuit or refitted to the pipe if it has fallen off.

Error CodePossible Fault
224Software issue. Arrange a visit from a Worcester Bosch engineer to reset the boiler/PCB.