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Worcester Bosch CDI Classic Combi boiler error codes
| Fault Description | System Behaviour |
| A1 Find a fix | Water is leaking or the pump needs replacing or freeing due to the pump running dry |
| A7 Find a fix | The hot water negative thermistor coefficient (NTC) sensor is defective – the hot water sensor or connecting leads need checking |
| A8 Find a fix | Break communication to FX sensor controls electrical connections need checking |
| B1 Find a fix | Code plug not detected |
| C6 Find a fix | Fan speed too low – the fan lead and connector need checking and may need replacing |
| E2 Find a fix | Central heating (CH) water flow negative thermistor coefficient (NTC) sensor defective check CH flow NTC sensor and connection leads |
| E9 Find a fix | Safety temperature limiter in central heating (CH) flow has tripped the system pressure or safety temperature limiter needs checking |
| EA Find a fix | 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 Find a fix | Internal error – electrical connector contacts or programmer interface module – check ignition leads are not loose |
| F7 Find a fix | Flame detected even though the appliance is switched off – check the electrode assembly is dry and the pcb and flue are clear |
| FA Find a fix | Flame detected after gas shut off – the gas valve needs checking – hire a Gas Safe installer |
| FD Find a fix | Reset button pressed by mistake – press reset button again |
Worcester Bosch CDI Highflow Combi boiler error codes
| Fault Description | System Behaviour |
| A1 Find a fix | Pump dry run detection or pump is running in air the system pressure needs checking |
| A5 Find a fix | Tank negative thermistor coefficient (NTC) defect |
| A7 Find a fix | Domestic hot water (DHW) negative thermistor coefficient (NTC) defect |
| A8 Find a fix | Energy Management System (EMS) communication error |
| B1 Find a fix | Code plug not detected |
| B2, B3, B4, B5, B6 Find a fix | Data error |
| B7 Find a fix | Burner control error |
| C6 Find a fix | Fan defect |
| D3 Find a fix | External temperature limiter |
| D5 Find a fix | Condensate pump failure |
| D6 Find a fix | Internal heat bank overflow |
| EA Find a fix | Flame not detected |
| E2 Find a fix | Primary negative thermistor coefficient (NTC) defect |
| E9 Find a fix | Safety temperature limiter in central heating (CH) flow stat tripped |
| F0 Find a fix | Internal error |
| F1 Find a fix | ROM fault |
| F7 Find a fix | Flame detected after appliance has been shut off |
| FA Find a fix | Flame detected after gas shut off |
| FD Find a fix | Reset button pressed – try pressing the reset button again |
Worcester Bosch CDi Compact / Greenstar 25/30 Si Combi / Greenstar 27/30 I system boiler error codes
| Fault Description | System Behaviour |
| T1 Find a fix | Ignition test – checking the igniter spark |
| T2 Find a fix | Fan test – checking the basic fan |
| T3 Find a fix | Pump test – checking the basic pump |
| T4 Find a fix | Three way valve test |
| T6 Find a fix | Ionisation oscillator test |
| 9A 362 Find a fix | error – incorrect HCM fitted |
| 9U 233 Find a fix | Heat Control Module (HCM) error – problem with code plug |
| B7 257 Find a fix | Internal error – possible control board problem |
| C6 215 Find a fix | Fan problem – fan running too fast |
| C7 214 Find a fix | Fan problem – fan not running |
| D1 240 Find a fix | Return sensor error – sensor may be wet or damaged |
| E2 222 Find a fix | Flow sensor short circuit error |
| E5 218 Find a fix | Flow temperature too high |
| E9 219 Find a fix | Safety sensor fault – temperature too high, sensor short circuit or open circuit |
| EA 227 Find a fix | No flame detected or flame signal loss during operation |
| F0 237 Find a fix | Internal error |
| F7 228 Find a fix | Flame error – false flame or flame detected before burner started |
| FA 306 Find a fix | False flame fault – flame detected after burner stop |
| FD 231 Find a fix | Mains power fault – electrical power interruption |
| FA 364 Find a fix | Gas valve EV2 leak test failed – gas valve leak |
| FB 365 Find a fix | Gas valve EV1 leak test failed |
| A1 281 Find a fix | Pump stuck or running with air in the system |
| C1 264 Find a fix | Airflow stopped during operation |
| C4 273 Find a fix | Airflow present during last 24 hour |
| D1 240 Find a fix | Return sensor short circuit |
| D4 271 Find a fix | Temperature difference between flow and safety sensor exceeds limit |
| E9 224 Find a fix | Max thermostat activated – flue gas thermostat overheat |
| EA 227 Find a fix | No ionisation detected after ignition |
| EF 349 Find a fix | Central heating boil detected – boiler operating at minimum burner load with temperature difference greater than 18°C between Flow & Return. |
| NO CODE 212 Find a fix | Safety or flow temperature rising too fast |
Worcester Bosch CDi Classic Regular Boiler Error Codes
| Fault Description | System Behaviour |
| B1 Find a fix | Code plug not detected |
| C6 Find a fix | Fan speed too low |
| E2 Find a fix | Central heating (CH) flow negative thermistor coefficient (NTC) sensor defective |
| E9 Find a fix | Safety temperature limiter in central heating (CH) flow has tripped |
| EA Find a fix | Flame not detected |
| F0 Find a fix | Internal error |
| F7 Find a fix | Flame detected even though appliance switched off |
| FA Find a fix | Flame detected after gas shut off |
| FD Find a fix | Reset button pressed by mistake |
Worcester Bosch Greenstar I Combi / System boiler error codes
| Fault Description | System Behaviour |
| 226 Find a fix | Service tool has been connected in the blocking error history menu |
| FD 231 Find a fix | The power has been interrupted during a lockout |
| C7 214 Find a fix | Fan does not run during the start up phase – fan harness connector needs checking |
| C6 215 Find a fix | Fan speed too high – check the fan harness and connector |
| C7 216 Find a fix | Fan speed too low – check the fan harness and connector |
| C7 217 Find a fix | Fan has stopped during appliance operation |
| C1 264 Find a fix | Fan stopped during operation |
| C4 273 Find a fix | Continuous fan operation for the last 24 hours – appliance temporarily blocked |
| E2 222 Find a fix | Flow temperature sensor shorted |
| E2 233 Find a fix | Flow temperature sensor disconnected |
| E9 276 Find a fix | Primary flow temperature exceeded 95°c |
| E2 350 Find a fix | Flow temperature sensor shorted |
| E2 351 Find a fix | Flow temperature sensor disconnected |
| FA 306 Find a fix | Ionisation detected after the gas valve closed |
| EA 227 Find a fix | No ionisation detected after ignition |
| F7 228 Find a fix | Isioniation current detected before burner start |
| EA 229 Find a fix | Loss of ionisation signal during operation |
| EA 261 Find a fix | Heat control module (HCM) potentially defective – reset the appliance |
| 9U 233 Find a fix | Control box or heat control module (HCM) is defective or loose, the HCM needs to be checked |
| C4 237 Find a fix | Control box or heat control module (HCM) is defective |
| F0 238 Find a fix | Gas valve or control box error – gas valve coils need checking |
| F0 239 Find a fix | Control box or the heat control module (HCM) is defective – the control box connections need checking |
| F0 242 Find a fix | Control box or the heat control module (HCM) is defective – the HCM and control box connections need to be checked |
| B7 257 Find a fix | Control box or the heat control module HCM) is defective- the HCM and control box connections need to be checked |
| F0 258 Find a fix | Control box or the heat control module (HCM) is defective – HCM or control box connections need to be checked |
| EH 258 Find a fix | Control box or the heat control module (HCM) is defective – HCM or control box connections need to be checked |
| F1 259 Find a fix | Control box or the heat control module (HCM) is defective – HCM or control box connections need to be checked |
| F0 262 Find a fix | Control box or the heat control module (HCM) is defective – HCM or control box connections need to be checked |
| F1 263 Find a fix | Control box or the heat control module (HCM) is defective – HCM or control box connections need to be checked |
| F0 272 Find a fix | 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 Find a fix | 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 Find a fix | Control box is defective – HCM needs checking as it might not be inserted properly or need replacing |
| 328 Find a fix | Internal error with the mains voltage – frequency may be inconsistent |
| 235 Find a fix | Incompatible heat control module (HCM) software versions – control box needs latest software |
| 356 Find a fix | Low mains voltage – the voltage may be interrupted or inconsistent and needs checking |
| 360 Find a fix | Heat control module (HCM) invalid – the inserted HCM does not correspond with the control box |
| A8 362 Find a fix | Low mains voltage – the voltage may be interrupted, inconsistent or heat control module (HCM) invalid |
| CC 800 Find a fix | Outdoor sensor defect available when accessory outdoor sensor is connected |
| A1 281 Find a fix | Pump stock or running dry |
| E9 224 Find a fix | Flue or high limit thermostat activated |
| D4 341 Find a fix | Primary flow temperature rising too fast |
Worcester Bosch GB162 Boiler Error Codes
| Fault Description | System Behaviour |
| 208 Find a fix | The boiler is in chimney sweep mode |
| 200 Find a fix | The boiler is in heating mode |
| 201 Find a fix | The boiler is in domestic hot water (DHW) mode |
| 202 Find a fix | The boiler is waiting – there was a heat demand from the on off or modulating control |
| 203 Find a fix | The boiler is on standby |
| 204 Find a fix | The boiler is waiting – the actual temperature is higher than the calculated or selected boiler temperature |
| 212 Find a fix | The temperature recorded by the flow temperature sensor or the safety sensor is rising too quickly |
| 226 Find a fix | Diagnosis tool was connected and is now locked out |
| 260 Find a fix | The flow temperature sensor is not detecting a rise in temperature following a burner start |
| 265 Find a fix | The boiler is waiting in response to a heat demand – the boiler regularly switches to partial load |
| 268 Find a fix | Component test phase |
| 270 Find a fix | The boiler is modulating upwards |
| 283 Find a fix | The boiler is preparing for a burner start – the fan and pump are activated |
| 284 Find a fix | The gas valve is switched |
| 305 Find a fix | The boiler is waiting for domestic hot water (DHW) operation to end |
| 235 Find a fix | The KIM (boiler identification module) is too new for the burner control unit |
| 360 Find a fix | The KIM that has been fitted is not compatible with the burner control unit |
| 9A 361 Find a fix | The burner control unit that has been fitted is not compatible with the KIM (boiler identification module) |
| 9U 233 Find a fix | The burner control unit or KIM (boiler identification module) is faulty |
| A3 317 Find a fix | Short circuit in the flue gas temperature sensor contacts |
| B7 257 Find a fix | The burner control unit or the KIM (boiler identification module) is faulty |
| C1 264 Find a fix | No control signal or power supply to the fan during operation |
| C4 273 Find a fix | The boiler was switched off for a maximum of 2 minutes because it had been operating continuously for more than 24 hours |
| C6 215 Find a fix | The fan speed is too high |
| C6 216 Find a fix | The fan speed is too low |
| C7 214 Find a fix | The fan does not run during the start phase |
| C7 217 Find a fix | The fan speed is irregular when starting up |
| CE 207 Find a fix | Water pressure is too low |
| CE 266 Find a fix | Pump test failed |
| D1 240 Find a fix | The contacts of the boiler return temperature sensor have been short circuited |
| D1 241 Find a fix | The contacts of the boiler return temperature sensor have been interrupted |
| D3 232 Find a fix | The external switching contact has opened |
| D4 213 Find a fix | The actual temperature recorded by the flow temperature sensor or return temperature sensor is rising too quickly |
| D4 271 Find a fix | Actual temperature differential between flow and safety temperature sensor is too high |
| D4 286 Find a fix | The boiler return temperature sensor has detected a return temperature higher than 105°c |
| E2 222 Find a fix | Short circuit in the flow temperature sensor contacts |
| E2 223 Find a fix | The flow temperature sensor contacts have been interrupted |
| E5 218 Find a fix | The temperature captured by the flow temperature sensor exceeded 105°c |
| E9 210 Find a fix | The temperature measured by the flue gas sensor is too high and is open |
| E9 219 Find a fix | The safety temperature sensor has captured a temperature in excess of 105°C |
| E9 220 Find a fix | The contacts for the safety temperature sensor have shorted or the safety temperature sensor has detected a temperature higher than 130°c |
| E9 224 Find a fix | The contacts of the safety temperature sensor have been interrupted |
| E9 276 Find a fix | The temperature flow sensor has measured a temperature in excess of 95°c |
| E9 277 Find a fix | The safety temperature sensor has measured temperature in excess of 95°c |
| E9 285 Find a fix | The boiler return temperature sensor has measured a temperature higher than 95°c |
| E9 318 Find a fix | The flue gas temperature sensor contacts have been interrupted |
| EA 227 Find a fix | An insufficient ionisation current was measured following ignition of the burner |
| EA 229 Find a fix | The ionisation current detected by the system during the burning phase was insufficient |
| EA 234 Find a fix | The contacts of the gas valve have been interrupted |
| EA 261 Find a fix | The burner control unit is faulty |
| EA 269 Find a fix | The ignition device has been activated for too long |
| F0 238 Find a fix | The burner control unit KIM (boiler identification module) is faulty |
| F0 239 Find a fix | 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 Find a fix | 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 Find a fix | The sensor test has failed – cabling and plug sensors need checking |
| F0 279 Find a fix | The burner control unit, or KIM, is faulty – control unit may need replacing |
| F0 280 Find a fix | The burner control unit is faulty |
| F0 287 Find a fix | The burner control unit, or KIM, has an error |
| F0 290 Find a fix | The burner control unit, or KIM, is faulty |
| F7 228 Find a fix | An ionisation current was measured before the burner started |
| F7 328 Find a fix | A brief power failure has occurred |
| FA 306 Find a fix | An ionisation current was measured after the burner went out |
| FD 231 Find a fix | The mains voltage was interrupted during an interlocking fault |
| EC 256 Find a fix | The burner control unit has an error |
| EH 258 Find a fix | The burner control unit is faulty – check the plug and wiring of the burner control unit. |
| H07 Find a fix | The current water pressure is too low, limiting the performance in heat mode as well as domestic hot water (DHW) mode |
| HrE Find a fix | The boiler keeps resetting |
| rE Find a fix | The boiler resets |
Worcester Bosch CDI Highflow Combi boiler error codes
A light on your boiler will flash to indicate that there is a fault. Depending on the type of fault, the light will flash in a different sequence.
There will be 4 quick flashes followed by a 5-second gap when the light is off and finally a series of longer flashes. The number of long flashes tells you which fault the boiler has.
| Fault Description | System Behaviour |
| Light off Find a fix | No boiler demand |
| Light on Find a fix | Heating demand on boiler is OK |
| 1 flash 5 seconds off Find a fix | No ionisation detected after ignition |
| 2 flashes 5 seconds off Find a fix | Loss of ionisation signal during operation |
| 3 flashes 5 seconds off Find a fix | Gas valve error |
| 4 flashes 5 seconds off Find a fix | First safety timing error / ignition timing error |
| 5 flashes 5 seconds off Find a fix | 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 Find a fix | Sensor test failed |
| 4 flashes, 5 second gap, 2 long flashes Find a fix | Safety temperature too high |
| 4 flashes, 5 second gap, 3 long flashes Find a fix | Max safety thermostat activated |
| 4 flashes, 5 second gap, 4 long flashes Find a fix | Return temperature too high |
| 4 flashes, 5 second gap, 5 long flashes Find a fix | Flow temperature too high – supply sensor exceeded 110°c |
| 1 long flash, 4 quick flashes, 5 second gap, 1 long flash, 4 quick flashes Find a fix | Heating control module (HCM) defective |
| 2 long flashes, 4 quick flashes, 5 second gap, 2 long flashes, 4 quick flashes Find a fix | 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 Find a fix | Mains voltage interrupted after locking error |
| 4 long flashes, 4 quick flashes, 5 second gap, 4 long flash, 4 quick flashes Find a fix | Internal control board faults |
| 5 long flashes, 4 quick flashes, 5 second gap, 5 long flash, 4 quick flashes Find a fix | All other miscellaneous faults – reset the boiler by turning the control knob anti-clockwise to the reset position |
Worcester Bosch Greenstar Ri Boiler Error Codes
| Fault Description | System Behaviour |
| No light Find a fix | No power at control board |
| Light on Find a fix | Appliance on but not operating during demand |
| Slow flash ( mostly off flashes on) Find a fix | Ignition lockout |
| Slow flash ( mostly on flashes off) Find a fix | Flue overheat or heat exchanger overheat |
| Fast flash Find a fix | Volatile lockout sensor fan or code plug |
| 2 pulses Find a fix | Check service mode switch is in minimum position |
| 5 pulses Find a fix | Check service mode switch is in max position |
Worcester Bosch Greenstar 8000 boiler error codes
| Fault Description | System Behaviour |
| 200 O Find a fix | Boiler in heating mode |
| 201 O Find a fix | Boiler in hot water mode |
| 202 O Find a fix | Boiler in anti-cycle mode |
| 203 0 Find a fix | Boiler in standby – no heat energy demand |
| 204 O Find a fix | Current primary water temperature higher than set value |
| 208 0 Find a fix | Chimney sweep demand |
| 224 V Find a fix | Safety temperature limiter has tripped – top-up water until the reset pressure is reached |
| 227 V Find a fix | No flame signal after ignition burner control unit could need replacing |
| 228 V Find a fix | Flame signal without flame present – air/gas ratio control valve may need replacing as might the ionisation cable |
| 305 0 Find a fix | Boiler in hot water anti-cycle mode |
| 306 V Find a fix | Flame signal after closing the fuel supply – the air/gas ratio control valve might need replacing |
| 360 V Find a fix | Incompatible code plug – check if a correct code plug is installed and exchange or reconnect code plug |
| Low loss header temperature sensor faulty – check the sensor port or check the differential sensor for incorrect installation position or breakage | |
| 1010 O Find a fix | 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 Find a fix | Water pressure too low – the water needs topping up and the vent system or pressure sensor may need replacing |
| 1021 B Find a fix | Hot water temperature sensor is defective – the plug to the hot water temperature sensor may not be connected |
| 1022 B Find a fix | 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 Find a fix | Outside temperature sensor is defective – check the connecting lead |
| 1065 B Find a fix | Pressure sensor defective or not connected – check pressure sensor connection as it may need replacing |
| 1068 W Find a fix | Outside temperature sensor defective – check the connecting lead |
| 1073 W Find a fix | Short circuit of the flow temperature sensor – the temperature sensor may need replacing |
| 1074 W Find a fix | 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 Find a fix | Short circuit of the temperature sensor at the heating block – temperature sensor may need replacing |
| 1076 W Find a fix | No signal from the temperature sensor at the heating block available – replace the temperature sensor, the connecting lead or the control unit |
| 2920 VFind a fix | Error with the flame monitoring |
| 2924 V Find a fix | 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 Find a fix | Feedback from the modulating gas valve is too low |
| 2927 B Find a fix | 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 Find a fix | Incorrect code plug detected – the code plug needs replacing |
| 2948 B Find a fix | 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 Find a fix | No flame signal. Following starting procedure the burner starts automatically. After cleaning set the correct gas / air ratio correctly |
| 2963 B Find a fix | Signal from flow and heat exchanger temperature sensor outside the permissible range – the connecting lead needs connecting correctly |
| 2964 B Find a fix | Flow rate in heat exchanger is too low |
| 2965 B Find a fix | Flow temperature too high |
| 2966 B Find a fix | Flow temperature rise in heat exchanger too rapid |
| 2967 B Find a fix | Flow / heat exchanger temperature sensor differential too great |
| 2970 B Find a fix | Pressure drop in heating system too rapid |
| 2971 B Find a fix | 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 |
