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Worcester Bosch Boiler Fault Codes Guide

Posted on 22nd January 2021 by H2 Property Services

Is your Worcester-Bosch boiler displaying seemingly random letters and numbers? These are known as ‘fault codes’ or ‘error codes’.

These codes appear when your boiler has experienced a fault, with each code representing a specific issue. You may be able to resolve some issues yourself, or you may need professional intervention from an experienced boiler engineer. Use this guide to find out your next steps to fixing your Worcester-Bosch boiler.

Worcester Bosch Boiler Fault Codes

Worcester Bosch Boilers

If you need boiler services across London, use a boiler engineer that you can trust. H2 Property Services have been fixing boilers for over 15 years. All our engineers are gas-safe certified and can fix boilers from all the leading manufacturers. Using your boiler’s fault code and our wealth of experience, we will locate and fix any problems quickly. We even offer emergency call-outs if your boiler needs immediate attention. Simply get in touch and we’ll be there.

For trusted boiler services in London, give our team a call today on 020 3858 8013. Or use our quick quote form!

Find your Worcester Bosch Boiler Model:

 


 

Worcester Bosch CDI Classic Combi Boiler Error Codes

 

Fault Code Reason(s)
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.

 

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Worcester Bosch CDI Highflow Combi Boiler Error Codes

 

Fault Code Reason(s)
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

 

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Worcester Bosch CDi Compact / Greenstar 25/30 Si Combi / Greenstar 27/30 I system Boiler Error Codes

 

Fault Code Reason(s)
T1 Ignition test – checking the igniter spark
T2 Fan test – checking the basic fan
T3 Pump test – checking the basic pump
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 – possible 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
D1 240 Return sensor short circuit
D4 271 Temperature difference between flow and safety sensor exceeds limit
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

 

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Worcester Bosch CDi Classic Regular Boiler Error Codes

 

Fault Code Reason(s)
B1 Code plug not detected
C6 Fan speed too 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 Reset button pressed by mistake

 

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Worcester Bosch Greenstar I System / Combi Boiler Error Codes

 

Fault Code Reason(s)
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

 

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Worcester Bosch GB162 Boiler Error Codes

 

Fault Codes Reason(s)
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

 

Need help with your Boiler? Call our Boiler Engineers on 020 3858 8013!

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Worcester Bosch CDI Highflow Combi Boiler Error Codes

 

Fault Code Reason(s)
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
Gas valve EV2 leak test failed
Gas valve EV1 leak test failed
Ionisation current detected before burner start
Gas valve error
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
Fan running too slow
No airflow after defined period of time
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

 

Need help with your Boiler? Call our Boiler Engineers on 020 3858 8013!

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Worcester Bosch Greenstar Ri Boiler Error Codes

 

Fault Code Reason(s)
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

 

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Worcester Bosch Greenstar 8000 Boiler Error Codes

 

Fault Code Reason(s)
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 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.

 

Worcester Bosch Boiler Engineers London

Our knowledge and exposure to all the different makes and models means that they are quickly able to diagnose faults and correctly identify parts for replacement. Our specialists can also make long-lasting repairs and carry out effective maintenance services.

This helps to ensure the length-of-life of your boiler is extended as long as possible. This allows us to pass on to our customers extended warranties of up to 8 years for their new boilers. We are experienced with all makes and models of boilers, and our friendly team are always happy to help.

Contact our team today on 020 3858 8013 for a quote.

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