MK City plumbing and heating install many boiler brands, including Baxi & Worcester Bosch. Baxi has been manufacturing boilers since 1866 and is considered a respected and trusted heating brand in the UK.
No one likes to be without heating and hot water. But, the reality is that boilers can fail anytime, causing worry and inconvenience at the most unpopular times. But, before you pick up your phone and call our Gas Safe engineers at MK City Plumbing and Heating, you may want to read our information below. It may help troubleshoot and determine the next best steps with your boiler, such as resolving the issue yourself or looking for a repair or replacement solution.
All boiler brands have the potential to break down, but it is important to note that having an annual boiler service can help reduce the problems you may have with your boiler. Here at MK City Plumbing and Heating, we encourage all our customers to ensure that their boiler is serviced every year to ensure that it continues to operate efficiently and maintain your boiler guarantee of warranty.
Need help with your Baxi Boiler?
MK City Plumbing & Heating is here to assist. We are the number one choice for all your plumbing and heating requirements. Give us a call on 01908 464 075, we are here to help!
MK City Plumbing & Heating are your local Baxi installers who have a wealth of expertise in installers, servicing and repairing Baxi boilers. In Milton Keynes and surrounding areas, we are known to be your go-to company for fault finding on Baxi boilers.
What are the common Baxi Boiler Fault Codes?
Error Code | Possible Fault |
| H.01 – .00 | Temporary Fault – Temporary loss of communication between the gas valve and boiler board. Fault in air/gas unit. Loose connection to the gas valve. |
| H.01 – .05 | Temporary Fault – Maximum difference between the flow and return temperature exceeded. Non-existent or insufficient circulation. Sensor error. |
| H.01 – .08 | Temporary Fault – Flow temperature increasing too fast in heating mode. Non-existent or insufficient circulation. Sensor error. |
| H.01 – .14 | Temporary Fault – Maximum flow temperature value exceeded. Non-existent or insufficient circulation. Non-existent or insufficient circulation. |
| H.01 – .18 | Temporary Fault – No circulation of water. Non-existent or insufficient circulation. Sensor error. |
| H.01 – .21 | Temporary Fault – Flow temperature increasing too fast in DHW mode. Non-existent or insufficient circulation. Sensor error. |
| H.02 – .02 | Temporary Fault – No input of parameters C1/C2. PCB not configured. |
| H.02 – .03 | Temporary Fault– Incorrect configuration settings C1/C2. |
| H.02 – .04 | Temporary Fault – Parameter error. Incorrect parameters. |
| H.02 – .06 | Temporary Fault – System water pressure. Water leak on the boiler. Water leak on the system. |
| H.03 -.00 | Temporary Fault – Communication error with NTC flue sensor. Sensor not, or badly connected. Bad connection. Sensor fault. |
| H.03 -.01 | Temporary Fault – Communication error with the HMI PCB. HMI is not connected. |
| H.03 -.02 | Temporary Fault – No flame during operation. No ionization current. |
| E.00 – .04 | Permanent Fault – Return temperature sensor open-circuit. Sensor not or badly connected. Bad connection. Sensor fault. |
| E.00 – .05 | Permanent Fault – Return temperature sensor open-circuit. Sensor not or badly connected. Bad connection. Sensor fault. |
| E.01 – .02 | Permanent Fault – Temperature measured by return sensor greater than flow sensor. Bad connection. Sensor fault. Sensor not or badly connected. |
| E.01 – .04 | Permanent Fault – Loss of flame detected 5 times in 24 hours (With burner on). No ionization current. |
| E.01 – .11 | Permanent Fault Requiring Reset – Incorrect fan speed. External draught over the boiler. Defective gas/air unit. |
| E.01 – .12 | Permanent Fault Requiring Reset – Temperature measured by return sensor greater than flow temperature. |
| E.01 – .17 | Permanent Fault Requiring Reset – No circulation. Sensor not or badly connected. Sensor fault. |
| E.01 – .20 | Permanent Fault – Maximum flue gas temperature value reached (>140 Deg C). No circulation. Sensor fault. |
| E.02 – .00 | Permanent Fault – Boiler reset in progress. Reset button has been pressed. |
| E.02 – .07 | No or low system water pressure. Low system pressure (less than 0.5bar) boiler will not function. |
| E.02 – .16 | Permanent Fault – Onboard CSU time-out. Check PCB for damage. |
| E.02 – .17 | Permanent Fault – Permanent loss of communication between the gas valve and boiler PCB. Fault in air/gas unit. Loose connection to the gas valve. |
| E.02 – .19 | Permanent Fault – Jumper 1 changed. Check the position of jumper 1. |
| E.02 – .20 | Permanent Fault – Jumper 2 changed. Check the position of jumper 2. |
| E.02 – .21 | Permanent Fault – Jumper 3 changed. Check the position of jumper 3. |
| E.02 – .47 | Permanent Fault – Connection to external device unsuccessful. Check wiring to external device. |
| E.02 – .48 | Permanent Fault – Configuration to external device unsuccessful. Check pairing to external. |
| E.04 – .00 | Permanent Fault – Gas valve fault. Gas valve not detected. |
| E.04 – .01 | Permanent Fault – Flow temperature sensor short-circuited. Sensor not or badly connected. Bad connection. Sensor fault. |
| E.04 – .02 | Permanent Fault – Flow temperature sensor open-circuited. Sensor not or badly connected. Bad connection. Sensor fault. |
| E.04 – .03 | Permanent Fault – Critical flow temperature reached. Non-existent or insufficient circulation. |
| E.04 – .04 | Permanent Fault – Flue temperature sensor short-circuited. Sensor not or badly connected. Bad connection. Sensor fault. |
| E.04 – .05 | Permanent Fault – Flue temperature sensor open-circuited. Sensor not or badly connected. Bad connection. Sensor fault. |
| E.04 – .06 | Permanent Fault – Critical flue gas temperature value reached. No circulation. Sensor fault. |
| E.04 – .08 | Permanent Fault – Maximum safe temperature value reached. (Safety thermostat open-circuited). No circulation. Sensor not or badly connected. Bad connection. Sensor fault. |
| E.04 – .10 | Failure to light (could be gas supply issue). |
| E.04 – .12 | Permanent Fault – False flame signal. Short-term fluctuation of the mains. Ionization current presents even though there is no flame. The burner remains very hot (CO2 is too high). Defective gas/air unit. |
| E.04 – .13 | Permanent Fault – Fan rotor blocked. Fan seized. Wiring to fan damaged. |
| E.04 – .17 | Permanent Fault – Problem with the gas valve. Defective gas/air unit. |
Error Code | Possible Fault |
| E20 | Central heating NTC fault |
| E28 | Flue NTC fault, air pressure switch fault, blocked flue, blocked condensate, or wiring fault. |
| E50 | Hot water NTC fault |
| E110 | E110 safety thermostat operated |
| E119 | The water pressure switch was not operated |
| E125 | Circulation fault (primary circuit) |
| E130 | Flue NTC operated |
| E133 | Interruption of gas supply or flame failure |
| E160 | Fan or fan wiring Fault |
| E193 | Pre-circulation fault |
Error Code | Possible Fault |
| E09 | Gas valve connection cable. |
| E10 | External probe fault. |
| E12 | Differential water flow switch fault (still open). |
| E13 | Differential water flow switch fault (still closed). |
| E15 | Gas valve command fault. |
| E20 | Central heating NTC fault. |
| E28 | Flue NTC fault. |
| E40 | Central heating return NTC fault. |
| E50 | DHW NTC sensor fault (tank boiler) (s.c.) OR DHW NTC sensor fault (tank boiler) (o.c.). |
| E83/E84/E85/E86/E87 | No communication. |
| E109 | Pre-circulation fault. |
| E110 | i) Boiler max temperature exceeded for gradient (probable pump jammed or air in the circuit). OR ii) Boiler max temperature exceeded for overtemperature (probable pump jammed or air in the circuit). OR iii) Safety thermostat sensor tripped. |
| E118 | Primary system water pressure too low (< 0.5 bar). |
| E125 | Circulation fault (primary). |
| E128 | Frequent flame failure (12 times). |
| E129 | Safety error for frequent loss of flame with max correction during the ignition during Calibration Function. |
| E130 | Flue thermostat sensor tripped (lockout). |
| E133 | Failure to light (could be a gas supply issue). |
| E134 | Elapsed time gas valve open without gas (short request in a short period) |
| E135 | Interruption of gas supply (internal error). |
| E154 | Flow/return sensor temperature test. |
| E160 | Fan or fan wiring fault |
| E163 | Domestic Hot Water NTC sensor fault (s.c.) OR Domestic Hot Water NTC sensor fault (o.c.). |
| E270 | Circulation fault (dry fire). |
| E317 | Wrong power supply electrical frequency (Hz). |
| E321 | Hot water NTC fault. |
| E384 | False flame. |
| E385 | Under voltage. |
| E430 | Water pressure temporary test. |
| E430 + Flame ‘crossed’ | Water pressure test failed. |
Error Code | Possible Fault |
| 1 flash green | Maximum flow temperature exceeded, Flow temperature rise rate too high, Excessive difference between, flow and return temperature |
| 2 flashes green | BL terminals on User Interaction, Controller are open circuit |
| 3 flashes green | No flame detected during operation |
| 4 flashes green | Bad connection or wiring fault, Internal communication fault |
| 5 flashes green | Parameter error or faulty PU, Configuration error or PCB fault |
| 6 flashes green | Possible fault. Internal fault in combustion control unit |
| 1 flash red | Bad connection to flow or return temperature sensor |
| 2 flashes red | Over-temperature thermostat on heat exchanger activated, No water flow through heat exchanger, PCB over-temperature condition, Flue fault resulting in recirculation or activation of air pressure switch (if fitted) |
| 3 flashes red | No ignition, No flame detected following ignition, False flame signal detected |
| 4 flashes red | Fan calibration error, Fan failure |
| 5 flashes red | Bad connection to PU, Parameter error or faulty PU |
| 6 flashes red | Possible fault. Bad connection or wiring fault, Parameter error |
Error Code | Possible Fault |
| E09 | Gas valve connection cable |
| E15 | Gas valve fault |
| E20 | Central heating NTC fault |
| E28 | Flue NTC fault |
| E40 | Central heating return NTC fault |
| E83 | Communication error |
| E109 | Pre-circulation fault |
| E110 | Safety thermostat operated |
| E118 | Primary system water pressure too low |
| E125 | Circulation fault (primary) |
| E128 | Flame failure |
| E130 | Flue NTC operated |
| E133 | Interruption of gas supply or flame failure |
| E135 | Interruption of gas supply (internal error) |
| E135 | Interruption of gas supply (internal error) |
| E154 | Flow/ return sensor temperature test |
| E160 | Fan or fan wiring fault |
| E270 | Circulation fault (Dry fire) |
| E321 | Hot water NTC fault |
| E384 | False flame |
Error Code | Possible Fault |
| E10 | Outdoor Sensor Error |
| E20 | Central Heating Thermistor Sensor Fault |
| E28 | Flue Thermistor Fault |
| E54 | HW Flow Sensor Fault |
| E78 | Water Pressure Sensor Fault |
| E100 | Internal Clock Time Error on PCB |
| E109 | Poor Circulation |
| 110 | Overheat |
| 111 | Maximum Limit of Flow Temperature |
| 117 | Water pressure too high |
| 118 | Water pressure too low |
| 119 | System Pressure Low (<0.5 bar) |
| 125 | Water circulation fault |
| 127 | Legionella Protection Temperature not reached |
| 128 | Loss of flame during operation |
| 133 | Safety time to establish flame exceeded |
| 153 | Forced reset unit unlocked |
| 160 | Fan Fault |
| 162 | Air pressure switch error |
| 164 | Heating flow switch error (Ireland) Pressure Sensor Error (UK) |
| 166 | Air Pressure Switch Fault |
| 270 | Dry Fire |
| 432 | Earth connector error |
| 433 | Heat exchanger temperature exceeded (greater than 95 degrees) |
Error Code | Possible Fault |
| 1 Green flash | Boiler temperature reached. No action required. |
| 3 Green flashes | Temporary flame loss. Boiler will self reset, if fault continues you will see 3 red flashes. |
| 4 Green flashes | Communication error between printed circuit board (PCB) and control. Temporary error, will self reset. |
| 5 Green flashes | Parameter error on printed circuit board (PCB). Temporary error, will self reset |
| 6 Green flashes | Miscellaneous error. Temporary error, will self reset. |
| 1 Red flash | Sensor Error; Sensor Fault, Temperature Fault or Flow Fault |
| 2 Red flashes | Boiler overheat tripped |
| 3 Red flashes | Ignition fault. Boiler has attempted to light 5 times and failed |
| 4 Red flashes | Fan Fault |
| 5 Red flashes | Parameter or PSU Error |
| 6 Red flashes | Miscellaneous error. |
Error Code | Possible Fault |
| E10 | Outdoor sensor error |
| E20 | Central Heating Thermistor Senor Fault |
| E28 | Flue Thermistor Fault |
| E110 | Boiler Overheat. Ensure radiators are bled of air |
| E119 | Low water pressure. Add water to the system via the filling loop |
| E125 | Primary Water Circulation Fault. Ensure radiators are bled of air |
| E131 | Flue overheat lock out. This may follow a power cut, try reset |
| E133 | Ignition fault – Check gas is turned on, if prepayment meter check there is credit. If all ok and E133 persists – contact Engineer to visit & investigate |
| E160/E161 | Fan Fault |
| E164 | Fan Fault |
| E167 | PCB Fault |
| E168 | PCB lock out |
| E193 | Circulation fault |
Error Code | Possible Fault |
| Flash Flash On | Fan Fault |
| Flash Off Flash | Incoming Voltage less than 180V |
| Flash Off On | Overheat lockout |
| Flash On Flash | PCB fault |
| Flash On On | PCB fault |
| Off Off Off | No power supply |
| On Flash Flash | No circulation/dry fire |
| On Flash On | Thermistor fault |
| On Off flash | Live and neutral reversed |
| On Off On | Ignition lockout |
| On Off Flash | PCB fault |
| On Off Flash | Low voltage wiring harness fault |
Error Code | Possible Fault |
| E4 | Ignition failure |
| E09 | Gas valve wiring fault |
| E10 | Outdoor sensor error |
| E15 | Gas valve connection fault |
| E20 | Central heating thermistor sensor fault |
| E28 | Flue thermistor fault |
| E40 | Central heating return thermistor fault |
| E53 | Flue obstruction |
| E55 | Calibration required |
| E78 | Water pressure sensor fault |
| E92 | Combustion test alarm during auto-setting |
| E109 | Poor circulation |
| E110 | Boiler overheat tripped |
| E117 | System pressure high (>2.9 Bar) |
| E118 | System pressure low (< 0.5bar) |
| E125 | Primary water circulation fault |
| E128 | Loss of flame during operation |
| E129 | Loss of flame during calibration |
| E133 | Ignition fault |
| E135 | Internal error |
| E154 | Primary flow fault |
| E160 | Fan fault |
| E270 | Dry fire |
| E317 | Wrong power supply (Hz) |
| E321 | Not water thermistor fault |
| E384 | Flame detected when gas valve off |
| E385 | Low voltage (less than 195v) |
Error Code | Possible Fault |
E0 | Temperature sensor fault |
E1 | Boiler overheat tripped |
E2 | Poor circulation |
E3 | PCB fault |
E4 | Ignition failure |
E10 | Poor/No circulation |
E12 | PCB Fault |
E13 | Heat exchanger thermal fuse tripped |
E83/84/85/86/87 | Fan fault normally E8 |
Error Code | Possible Fault |
1 Green Flash | Boiler temp reached |
3 Green Flashes | Boiler temp reached.Temporary error, self-reset, if continues will go to 3 red flashes |
3 Green Flashes | Temporary Flame Loss. Temporary error, self-reset, if continues will go to 3 red flashes |
4 Green Flashes | Communication error between PCB and Control. Temporary error, self-reset. |
5 Green Flashes | Parameter Error On PSU/PCB. Temporary error, self-reset. |
6 Green Flashes | Miscellaneous Error. Temporary error, self-reset. |
1 Red Flash | Sensor Error; Sensor Fault, Temperature Fault or Flow Fault |
2 Red Flashes | Boiler overheat tripped |
3 Red Flashes | Ignition fault. Boiler has attempted to light 5 times and failed |
4 Red Flashes | Fan Fault |
5 Red Flashes | Parameter or PSU Error |
6 Red Flashes | Miscellaneous |
Checkatrade Registered
At MK City Plumbing & Heating we are registered with Checkatrade, so that any of customers can read feedback from previous work we have completed. With a perfect 10 / 10 score, we work hard to ensure that time after time we provide an exceptional customer experience
Are you interested in replacing your boiler and avoiding recurrent Baxi boiler problems?
MK City Plumbing & Heating specialist is here to assist .If there is a problem, one of our highly skilled repair technicians will be on hand to figure it out quickly and efficiently. Whether or not you need a new boiler, our experts can help you with this decision.
Get in touch with us today by calling 01908 464 075 or browse our site for additional information.
Do you need Boiler Finance?
We know that you may need a new energy-efficient boiler, but funds are unavailable. So, we offer a range of finance options to help cover the cost of your new boiler and installation.
All our engineers are Gas Safe registered, and we prioritise all boiler breakdowns to help get you warm and comfortable again as quickly as possible.
What areas do we cover?
When you have a Baxi fault code issue, you want a local professional heating company to come and fix your Baxi boiler as quickly as possible. At MK City Plumbing and Heating, we always prioritise all emergencies when no hot water or heating is available
Our Gas Safe engineers are proud to support our local community in Milton Keynes, Bedford, Buckingham, Corby, Northampton, Leighton Buzzard and Kettering.
