Baxi boilers are renowned for their reliability and efficiency, but like all complex appliances, they can occasionally encounter issues.
When something goes wrong, your Baxi boiler will display an error code to help you diagnose the problem quickly. Understanding these error codes can save you time and money by allowing you to troubleshoot minor issues yourself or communicate effectively with a Gas Safe registered engineer.
In this guide, we'll explore the most common Baxi boiler error codes across various models. We'll provide clear explanations and possible causes to help you get your heating system back up and running.
Baxi boiler fault and error codes by model
Here’s a detailed guide to Baxi boiler error codes, categorised by model. These codes provide insight into specific issues, allowing for timely maintenance or repairs.
Baxi Platinum error codes
Baxi Platinum boilers are known for their efficiency and durability. Below is a list of common error codes for this model.
| Fault Code | Possible Cause |
|---|---|
| E20 | Central heating NTC (Negative Temperature Coefficient) thermistor error. |
| E28 | Flue NTC thermistor error. Possible air pressure switch fault, blocked flue or condensate pipe, or wind fault affecting the flue. |
| E50 | Hot water NTC thermistor error. |
| E110 | Safety thermostat activated due to overheating. |
| E119 | Water pressure switch not operated—indicates low water pressure. |
| E125 | Primary circuit circulation fault—could be due to pump failure or airlock. |
| E130 | Flue NTC thermistor activated—flue gas overheating. |
| E133 | Gas supply issue or flame failure detected. |
| E160 | Fan fault or fan wiring error. |
| E193 | Pre-circulation fault—issue with the pump or circulation. |
Baxi EcoBlue Error Codes
The Baxi EcoBlue range offers compact and efficient boilers, but like all systems, they can experience faults. Here’s a breakdown of common error codes.
| Fault Code | Possible Cause |
|---|---|
| 110 | Boiler overheated—try bleeding your radiators to release trapped air. |
| 117 | Water pressure too high—should be between 1.0 and 2.0 bar. |
| 118 | Water pressure too low—below 0.5 bar; needs repressurising. |
| 125 | Water circulation fault—possible pump issue or airlock in the system. |
| 133 | Safety time to establish flame exceeded—possible gas supply issue or ignition fault. |
| E10 | Outdoor sensor error—sensor faulty or not connected properly. |
| E20 | Central heating thermistor sensor fault—could be short-circuited or disconnected. |
| E28 | Flue thermistor fault—sensor issue or flue blockage. |
| E54 | Domestic hot water (DHW) flow sensor fault—sensor faulty or wiring issue. |
| E78 | Water pressure sensor fault—sensor malfunctioning or not connected properly. |
| E100 | Internal clock time error on printed circuit board (PCB)—PCB may need resetting or replacing. |
| E109 | Poor circulation—possible pump failure or blockage in the system. |
| 111 | Maximum limit of flow temperature exceeded—boiler is too hot; may indicate a sensor fault or circulation issue. |
| 119 | System pressure too low—needs to be increased to the recommended level. |
| 127 | Legionella protection temperature not reached—water not heated to sufficient temperature to kill bacteria. |
| 128 | Loss of flame during operation—possible gas supply issue or ignition fault. |
| 153 | Forced reset unit unlocked—manual reset required. |
| 160 | Fan fault—fan not operating correctly or wiring issue. |
| 162 | Air pressure switch error—faulty switch or blocked flue. |
| 164 | Pressure sensor error (UK) or heating flow switch error (Ireland)—sensor may be faulty or disconnected. |
| 166 | Air pressure switch fault—switch not responding as expected. |
| 270 | Dry fire—boiler has detected low water levels; may need repressurizing. |
| 432 | Earth connector error—possible electrical issue; check connections. |
| 433 | Heat exchanger temperature exceeded (greater than 95°C)—possible circulation issue or sensor fault. |
Baxi EcoBlue Advance / Ecoblue Regular Gas Boiler Flashing Light error codes
The Baxi EcoBlue Advance and Regular models use flashing lights to indicate faults. The number and color of flashes can help diagnose the issue.
| Fault Code | Possible Cause |
|---|---|
| 1 green flash | Boiler temperature reached set point. No action required. |
| 3 green flashes | Temporary flame loss. Boiler will self-reset. If the fault continues, it will display 3 red flashes. |
| 4 green flashes | Communication error between PCB and control. Temporary error; boiler should self-reset. |
| 5 green flashes | Parameter error on PCB. Temporary error; boiler should self-reset. |
| 6 green flashes | Miscellaneous error. Temporary error; boiler should self-reset. |
| 1 red flash | Sensor error—temperature fault or flow fault. Boiler may need resetting or sensor may need replacing. |
| 2 red flashes | Boiler overheat tripped. Allow boiler to cool and reset. If it persists, bleed radiators or check circulation. |
| 3 red flashes | Ignition fault—boiler has attempted to light 5 times and failed. Check gas supply or call an engineer. |
| 4 red flashes | Fan fault—fan not operating correctly; may need professional inspection. |
| 5 red flashes | Parameter storage unit (PSU) error—issue with settings storage; may need engineer to reprogram or replace PSU. |
| 6 red flashes | Miscellaneous error—boiler requires resetting or professional diagnosis. |
Baxi Duo-tec/Megaflo error codes
Below are common error codes for the Baxi Duo-tec and Megaflo boiler models.
| Fault Code | Possible Cause |
|---|---|
| E10 | Outdoor sensor fault—sensor may be faulty or disconnected. |
| E20 | Central heating thermistor sensor error—sensor issue causing incorrect temperature readings. |
| E28 | Flue thermistor error—possible blockage in flue or sensor fault. |
| E110 | Boiler overheat error—boiler temperature too high; may need bleeding or circulation checked. |
| E119 | Low water pressure error—pressure below required level; needs repressurizing. |
| E125 | Primary water circulation error—possible pump failure or airlock. |
| E131 | Flue overheat lockout error—flue gases too hot; may indicate blockage or sensor fault. |
| E133 | Ignition error—boiler failed to ignite; could be gas supply issue or ignition fault. |
| E160 / E161 | Fan error—fan not running correctly or wiring issue. |
| E164 | Pressure sensor fault—sensor not reading correctly; may need replacing. |
| E167 | PCB error—issue with the printed circuit board; may require professional attention. |
| E168 | PCB lockout error—boiler has locked out due to a PCB fault. |
| E193 | Circulation error—issue with water flow in the system; check pump and radiators. |
Baxi 200 / 400 Combi Gas Boiler error codes
The Baxi 200 and 400 Combi boilers are compact and efficient. They use a combination of letters and numbers to indicate faults.
| Fault Code | Possible Cause |
|---|---|
| H.01 – .00 | Loss of communication between gas valve and boiler board—possible fault in air/gas unit or loose connection to gas valve. |
| H.01 – .05 | Difference between flow and return temperature too high—sensor error or insufficient circulation. |
| H.01 – .08 | Sensor fault—flow temperature increasing too fast in heating mode; could indicate insufficient circulation. |
| H.01 – .14 | Maximum flow temperature value exceeded—temporary fault due to insufficient circulation. |
| H.01 – .18 | No water circulation—insufficient circulation or sensor error. |
| H.01 – .21 | Temporary error—flow temperature increasing too fast in DHW mode; check for circulation issues or sensor faults. |
| H.02 – .02 | Temporary error—no input of parameters C1/C2; PCB not configured properly. |
| H.02 – .03 | Temporary error—incorrect configuration settings C1/C2. |
| H.02 – .04 | Temporary error—parameter fault; incorrect settings. |
| H.02 – .06 | Temporary error caused by system water pressure—possible water leak in boiler or system. |
| H.03 – .00 | Temporary communication error with NTC or flue sensor—sensor may be unconnected or have a bad connection. |
| H.03 – .01 | Communication error with the PCB. |
| H.03 – .02 | Flame error—no flame detected during operation. |
| E.00 – .04 | Return temperature sensor open-circuit—sensor not connected or faulty. |
| E.00 – .05 | Return temperature sensor short-circuit—sensor may be damaged or improperly connected. |
| E.01 – .02 | Temperature measured by return sensor greater than flow sensor—possible sensor fault or reversed connections. |
| E.01 – .04 | Loss of flame detected 5 times in 24 hours—possible gas supply issue or ignition fault. |
| E.01 – .11 | Incorrect fan speed—external draught over the boiler or defective gas/air unit. |
| E.01 – .12 | Requires reset—temperature measured by return sensor greater than flow temperature; check sensors and circulation. |
| E.01 – .17 | Reset the boiler—no circulation; sensor fault either not connected or has a bad connection. |
| E.01 – .20 | Maximum flue gas temperature reached—no circulation or sensor fault. |
| E.02 – .00 | Reset button has been pressed—boiler is resetting. |
| E.02 – .07 | No or low system water pressure—system pressure less than 0.5 bar; needs repressurizing. |
| E.02 – .16 | Permanent fault caused by channel service unit (CSU) time-out or PCB damage. |
| E.02 – .17 | Loss of communication between gas valve and boiler PCB or fault in air/gas unit. |
| E.02 – .19 | Jumper 1 changed—check position of jumper 1 on the PCB. |
| E.02 – .20 | Jumper 2 changed—check position of jumper 2 on the PCB. |
| E.02 – .21 | Jumper 3 changed—check position of jumper 3 on the PCB. |
| E.02 – .47 | Wiring to external device error—check connections to external controls or devices. |
| E.02 – .48 | Configuration to external device unsuccessful—check pairing or settings with external device. |
| E.04 – .00 | Gas valve error—gas valve not detected; could be a wiring issue or faulty valve. |
| E.04 – .01 | Flow temperature sensor short-circuited—sensor not connected properly or faulty. |
| E.04 – .02 | Flow temperature sensor open-circuited—sensor not connected properly or faulty. |
| E.04 – .03 | Critical flow temperature reached—non-existent or insufficient circulation. |
| E.04 – .04 | Flue temperature sensor short-circuited—sensor not connected properly or faulty. |
| E.04 – .05 | Flue temperature sensor open-circuited—sensor not connected properly or faulty. |
| E.04 – .06 | Critical flue gas temperature value reached—no circulation or sensor fault. |
| E.04 – .08 | Maximum safe temperature value reached—safety thermostat open-circuited; no circulation or sensor fault. |
| E.04 – .10 | Failure to light—could be a gas supply issue or ignition fault. |
| E.04 – .12 | False flame signal—ionisation current detected without flame; possible short-term fluctuation or defective gas/air unit. |
| E.04 – .13 | Fan rotor blocked—fan seized or wiring to fan damaged. |
| E.04 – .17 | Problem with gas valve or defective gas/air unit—may need professional inspection or replacement. |
Baxi 600 Combi Gas Boiler fault codes
The Baxi 600 Combi is a compact and high-efficiency boiler. If you encounter an error code, refer to the table below.
| Fault Code | Possible Cause |
|---|---|
| E09 | Gas valve connection cable fault—check wiring to gas valve. |
| E10 | External probe fault—sensor may be faulty or disconnected. |
| E12 | Differential water flow switch fault (still open)—switch may be stuck or faulty. |
| E13 | Differential water flow switch fault (still closed)—switch may be stuck or faulty. |
| E15 | Gas valve command fault—issue with gas valve operation; may need replacing. |
| E20 | Central heating NTC thermostat fault—sensor issue causing incorrect temperature readings. |
| E28 | Flue NTC thermostat fault—sensor issue or flue blockage. |
| E40 | Central heating return NTC thermostat fault—sensor may be faulty or disconnected. |
| E50 | DHW NTC thermostat sensor fault—sensor short-circuited (s.c.) or open-circuited (o.c.); may need replacing. |
| E83/E84/E85/E86/E87 | No communication—issues with PCB or wiring; may need professional diagnosis. |
| E109 | Pre-circulation fault—issue with pump or blockage in the system. |
| E110 | Boiler max temperature exceeded—probable pump jammed or air in the circuit; safety thermostat may have tripped. |
| E118 | Primary system water pressure too low (< 0.5 bar)—needs repressurizing. |
| E125 | Circulation fault (primary)—possible pump failure or airlock. |
| E128 | Frequent flame failure (12 times)—possible gas supply issue or ignition fault. |
| E129 | Safety error due to frequent loss of flame with max correction during ignition—may need professional attention. |
| E130 | Flue thermostat sensor tripped (lockout)—flue gases too hot; may indicate blockage or sensor fault. |
| E133 | Failure to light—possible gas supply issue or ignition fault. |
| E134 | Elapsed time gas valve open without gas—short request in a short period; may indicate gas supply issue. |
| E135 | Interruption of gas supply (internal error)—possible gas valve or PCB issue. |
| E154 | Flow/return sensor temperature test—sensors may need checking or replacing. |
| E160 | Fan or fan wiring fault—fan not operating correctly; may need professional inspection. |
| E163 | DHW NTC thermostat sensor fault (s.c. or o.c.)—sensor may be faulty or disconnected. |
| E270 | Circulation fault (dry fire)—boiler has detected low water levels; may need repressurizing or pump inspection. |
| E317 | Wrong power supply electrical frequency (Hz)—check electrical supply; may need professional electrician. |
| E321 | Hot water NTC fault—sensor issue affecting hot water temperature readings. |
| E384 | False flame detected—ionisation current detected without flame; possible PCB or gas valve issue. |
| E385 | Under voltage—electrical supply voltage too low; contact electricity provider. |
| E430 | Water pressure temporary test—boiler is testing water pressure; no action required unless accompanied by other errors. |
| E430 + Flame ‘crossed’ | Water pressure test failed—system pressure issue; may need repressurising or leak inspection. |
Baxi MainEco error codes
The Baxi MainEco is designed for ease of use and efficiency. Flashing lights indicate error codes on this model.
| Fault Code | Possible Cause |
|---|---|
| 1 Green Flash | Boiler temperature reached set point—no action required. |
| 3 Green Flashes | Temporary flame loss—boiler should self-reset. If fault persists, professional attention may be needed. |
| 4 Green Flashes | Communication error between PCB and control—temporary error; boiler should self-reset. |
| 5 Green Flashes | Parameter error on PSU or PCB—temporary error; boiler should self-reset. |
| 6 Green Flashes | Miscellaneous error—temporary error; boiler should self-reset. |
| 1 Red Flash | Sensor error—temperature fault or flow fault; boiler may need resetting or sensor may need replacing. |
| 2 Red Flashes | Boiler overheat tripped—allow boiler to cool and reset. If it persists, bleed radiators or check circulation. |
| 3 Red Flashes | Ignition fault—boiler has attempted to light 5 times and failed; check gas supply or call an engineer. |
| 4 Red Flashes | Fan fault—fan not operating correctly; may need professional inspection. |
| 5 Red Flashes | PSU error—issue with settings storage; may need engineer to reprogram or replace PSU. |
| 6 Red Flashes | Miscellaneous error—boiler requires resetting or professional diagnosis. |
Baxi Avanta Range fault codes
The Baxi Avanta range includes compact boilers suitable for various home sizes. If you encounter an error, refer to the table below.
| Fault Code | Possible Cause |
|---|---|
| E0 | Temperature sensor fault—sensor may be faulty or disconnected. |
| E1 | Overheated—try bleeding your radiators to release trapped air. |
| E2 | Poor circulation—possible pump issue or blockage; try bleeding your radiators. |
| E3 | PCB fault—issue with the printed circuit board; may require professional attention. |
| E4 | Ignition failure—boiler failed to ignite; could be gas supply issue or ignition fault. |
| E10 | Poor or no circulation—check pump operation and bleed radiators. |
| E12 | PCB fault—issue with the printed circuit board; may require professional attention. |
| E13 | Heat exchanger thermal fuse tripped—boiler has overheated; may indicate circulation issues. |
| E83 / E84 / E85 / E86 / E87 | Fan fault—typically displayed as E8; fan may not be operating correctly or wiring issue. |
Baxi GA Range error codes
The Baxi GA range includes high-efficiency boilers with advanced controls. Below are common error codes for this range.
| Fault Code | Possible Cause |
|---|---|
| E53 | Poor combustion—flue terminal may be blocked; check for obstructions. |
| E110 | Overheated—try bleeding your radiators to release trapped air. |
| E117 | System water pressure high—should be between 1.0 and 2.0 bar; try bleeding water from your radiators. |
| E118 | System water pressure low—below 0.5 bar; needs repressurizing. |
| E125 | Overheat—possible circulation issue; try bleeding your radiators. |
| E133 | Gas supply fault—boiler not receiving gas; check gas supply or contact provider. |
| E4 | Ignition failure—boiler failed to ignite; could be gas supply issue or ignition fault. |
| E09 | Gas valve wiring fault—check wiring to gas valve. |
| E10 | Outdoor sensor error—sensor may be faulty or disconnected. |
| E15 | Gas valve connection fault—issue with gas valve operation; may need replacing. |
| E20 | Central heating thermistor sensor fault—sensor issue causing incorrect temperature readings. |
| E28 | Flue thermistor fault—sensor issue or flue blockage. |
| E40 | Central heating return thermistor fault—sensor may be faulty or disconnected. |
| E55 | Calibration required—boiler needs to be calibrated; may require professional service. |
| E78 | Water pressure sensor fault—sensor malfunctioning or not connected properly. |
| E92 | Combustion test alarm during auto-setting—may require professional attention. |
| E109 | Poor circulation—possible pump failure or blockage in the system. |
| E128 | Loss of flame during operation—possible gas supply issue or ignition fault. |
| E129 | Loss of flame during calibration—may need professional attention. |
| E135 | Internal error—possible PCB or gas valve issue. |
| E154 | Primary flow fault—issue with water flow; check pump and circulation. |
| E160 | Fan fault—fan not operating correctly; may need professional inspection. |
| E270 | Dry fire—boiler has detected low water levels; may need repressurizing or pump inspection. |
| E317 | Wrong power supply (Hz)—check electrical supply; may need professional electrician. |
| E321 | Hot water thermistor fault—sensor issue affecting hot water temperature readings. |
| E384 | Flame detected when gas valve off—possible gas valve fault or PCB issue. |
| E385 | Low voltage (less than 195V)—electrical supply voltage too low; contact electricity provider. |
Baxi Solo fault codes
The Baxi Solo is a range of conventional boilers. Error codes are indicated through a combination of flashing lights.
| Fault Code | Possible Cause |
|---|---|
| FLASH FLASH ON | Fan error—fan not operating correctly; may need professional inspection. |
| FLASH OFF FLASH | Voltage less than 180V—electrical supply voltage too low; contact electricity provider. |
| FLASH OFF ON | Overheat lockout—boiler has overheated; allow to cool and reset. |
| FLASH ON FLASH | PCB error—issue with the printed circuit board; may require professional attention. |
| FLASH ON ON | PCB fault—printed circuit board may need replacing. |
| OFF OFF OFF | No power—check electrical supply and fuses. |
| ON FLASH FLASH | Circulation error or dry fire—check pump operation and system pressure. |
| ON FLASH ON | Thermistor error—temperature sensor fault; may need replacing. |
| ON OFF FLASH | Live and neutral reversed error—electrical wiring issue; consult a professional electrician. |
| ON OFF ON | Ignition lockout error—boiler failed to ignite; could be gas supply issue or ignition fault. |
| ON ON FLASH | PCB error—issue with the printed circuit board; may require professional attention. |
| ON ON ON | Low voltage wiring harness error—issue with wiring; may need professional inspection. |
Error code E133 and E28
If you're seeing E133 or E28 error codes on your Baxi boiler, it's likely due to a frozen condensate pipe. In cold weather, the condensate pipe, which runs outside, can freeze and block, causing these errors.
How to fix
- Thaw the condensate pipe: Gently pour warm (not boiling) water over the pipe to melt the ice blockage. Alternatively, use a hot water bottle or heat wrap as a compress.
- Reset the boiler: Once the pipe is clear, reset your boiler to see if it resumes normal operation.
When to call a professional
Some boiler problems can be solved with a few simple checks, but anything involving the gas supply, the inside of the boiler, or a fault that keeps coming back needs a Gas Safe registered engineer. Never remove the boiler casing or attempt internal repairs yourself.
JustFix engineers can diagnose the fault, explain what's needed and what it'll cost before any work starts, and get your heating and hot water back up and running. All our work is backed by our 12-month workmanship guarantee.
Need a hand? Tell us what's going on and we'll take it from there.
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