Complete reference guide for all Baxi boiler fault codes. Find your error code below for detailed causes and step-by-step solutions. Baxi boilers include Platinum, EcoBlue, Duo-tec, 200/400 series, 600 series, and more.
Listed below are all Baxi fault codes as described by the boiler manufacturer along with possible causes. Click “View Solution” for detailed step-by-step fixes, DIY tips, and when to call a Gas Safe engineer.
Baxi boilers display fault codes differently depending on the model:
– Digital displays show alphanumeric codes (E133, E119, H.01, etc.)
– Older models use flashing LED lights to indicate faults
– Find your boiler model below and locate your fault code
| Fault Code | Possible Cause | Solution |
|---|---|---|
| E20 | Central heating NTC error | View Solution → |
| E28 | Flue NTC error, air pressure switch, blocked flue or condensate | View Solution → |
| E50 | Hot water NTC error | View Solution → |
| E110 | Thermostat operated safety | View Solution → |
| E119 | Water pressure switch error – not operated | View Solution → |
| E125 | Primary circuit circulation fault | View Solution → |
| E130 | Flue NTC operation error | View Solution → |
| E133 | Gas supply error or flame failure | View Solution → |
| E160 | Fan or fan wiring error | View Solution → |
| E193 | Pre-circulation error | View Solution → |
| Fault Code | Possible Cause | Solution |
|---|---|---|
| E10 | Outdoor sensor error | View Solution → |
| E20 | Central heating thermistor sensor fault | View Solution → |
| E28 | Flue thermistor fault | View Solution → |
| E54 | DHW flow sensor fault | View Solution → |
| E78 | Water pressure sensor fault | View Solution → |
| E100 | Internal clock time error on PCB | View Solution → |
| E109 | Poor circulation | View Solution → |
| 110 | Overheat – try bleeding radiators | View Solution → |
| 111 | Maximum limit of flow temperature | View Solution → |
| 117 | Water pressure too high | View Solution → |
| 118 | Water pressure too low | View Solution → |
| 119 | System pressure too low | View Solution → |
| 125 | Water circulation fault | View Solution → |
| 127 | Legionella protection temperature not reached | View Solution → |
| 128 | Loss of flame during operation | View Solution → |
| 133 | Safety time to establish flame exceeded | View Solution → |
| 153 | Forced reset unit unlocked | View Solution → |
| 160 | Fan fault | View Solution → |
| 162 | Air pressure switch error | View Solution → |
| 164 | Pressure sensor error / heating flow switch error | View Solution → |
| 166 | Air pressure switch fault | View Solution → |
| 270 | Dry fire | View Solution → |
| 432 | Earth connector error | View Solution → |
| 433 | Heat exchanger temperature exceeded (>95°C) | View Solution → |
Note: If your EcoBlue has no digital display, use these LED patterns:
| LED Pattern | Fault | Solution |
|---|---|---|
| 1 green flash | Boiler temperature reached – normal operation | No action required |
| 3 green flashes | Temporary flame loss – will self reset | View Solution → |
| 4 green flashes | Communication error between PCB and control | View Solution → |
| 5 green flashes | Parameter error on PCB | View Solution → |
| 6 green flashes | Miscellaneous error | View Solution → |
| 1 red flash | Sensor error, temperature fault or flow fault | View Solution → |
| 2 red flashes | Boiler overheat tripped | View Solution → |
| 3 red flashes | Ignition fault – 5 failed attempts | View Solution → |
| 4 red flashes | Fan fault | View Solution → |
| 5 red flashes | PSU (Parameter Storage Unit) error | View Solution → |
| 6 red flashes | Miscellaneous error | View Solution → |
| Fault Code | Possible Cause | Solution |
|---|---|---|
| E10 | Outdoor sensor fault | View Solution → |
| E20 | Central heating thermistor sensor error | View Solution → |
| E28 | Flue thermistor error | View Solution → |
| E110 | Boiler overheat error | View Solution → |
| E119 | Low water pressure error | View Solution → |
| E125 | Primary water circulation error | View Solution → |
| E131 | Flue overheat lockout error | View Solution → |
| E133 | Ignition error | View Solution → |
| E160 / E161 | Fan error | View Solution → |
| E164 | Pressure sensor fault | View Solution → |
| E167 | Printed circuit board (PCB) error | View Solution → |
| E168 | PCB lockout error | View Solution → |
| E193 | Circulation error | View Solution → |
| Fault Code | Possible Cause | Solution |
|---|---|---|
| H.01-.00 | Loss of communication between gas valve and board | View Solution → |
| H.01-.05 | Flow/return temperature difference too high | View Solution → |
| H.01-.08 | Flow temperature increasing too fast | View Solution → |
| H.01-.14 | Maximum flow temperature value exceeded | View Solution → |
| H.01-.18 | No water circulation or sensor error | View Solution → |
| H.01-.21 | Flow temperature rising too fast in DHW mode | View Solution → |
| H.02-.02 | No input of parameters C1/C2 – PCB not configured | View Solution → |
| H.02-.03 | Incorrect configuration settings C1/C2 | View Solution → |
| H.02-.04 | Parameter fault – incorrect parameters | View Solution → |
| H.02-.06 | System water pressure error or leak | View Solution → |
| H.03-.00 | Communication error with NTC or flue sensor | View Solution → |
| H.03-.01 | Communication error with PCB | View Solution → |
| H.03-.02 | Flame error – no flame during operation | View Solution → |
| E.00-.04 | Return temperature sensor open-circuit | View Solution → |
| E.00-.05 | Return temperature sensor short-circuit | View Solution → |
| E.01-.02 | Return sensor temperature greater than flow | View Solution → |
| E.01-.04 | Loss of flame 5 times in 24 hours | View Solution → |
| E.01-.11 | Incorrect fan speed | View Solution → |
| E.01-.12 | Return sensor higher than flow temperature | View Solution → |
| E.01-.17 | No circulation or sensor fault | View Solution → |
| E.01-.20 | Maximum flue gas temperature reached | View Solution → |
| E.02-.00 | Reset button pressed | View Solution → |
| E.02-.07 | No or low system water pressure (<0.5 bar) | View Solution → |
| E.02-.16 | CSU timeout or PCB damage | View Solution → |
| E.02-.17 | Loss of communication or air/gas unit fault | View Solution → |
| E.02-.19 | Jumper 1 changed – check position | View Solution → |
| E.02-.20 | Jumper 2 changed – check position | View Solution → |
| E.02-.21 | Jumper 3 changed – check position | View Solution → |
| E.02-.47 | Wiring to external device error | View Solution → |
| E.02-.48 | Configuration to external device unsuccessful | View Solution → |
| E.04-.00 | Gas valve error – not detected | View Solution → |
| E.04-.01 | Flow temperature sensor short-circuited | View Solution → |
| E.04-.02 | Flow temperature sensor open-circuited | View Solution → |
| E.04-.03 | Critical flow temperature – insufficient circulation | View Solution → |
| E.04-.04 | Flue temperature sensor short-circuited | View Solution → |
| E.04-.05 | Flue temperature sensor open-circuited | View Solution → |
| E.04-.06 | Critical flue gas temperature – no circulation | View Solution → |
| E.04-.08 | Maximum safe temperature – safety thermostat open | View Solution → |
| E.04-.10 | Failure to light – possible gas supply issue | View Solution → |
| E.04-.12 | False flame signal | View Solution → |
| E.04-.13 | Fan rotor blocked or seized | View Solution → |
| E.04-.17 | Gas valve or gas/air unit problem | View Solution → |
| Fault Code | Possible Cause | Solution |
|---|---|---|
| E09 | Gas valve connection cable fault | View Solution → |
| E10 | External probe fault | View Solution → |
| E12 | Differential water flow switch fault (still open) | View Solution → |
| E13 | Differential water flow switch fault (still closed) | View Solution → |
| E15 | Gas valve command fault | View Solution → |
| E20 | Central heating NTC thermostat fault | View Solution → |
| E28 | Flue NTC thermostat fault | View Solution → |
| E40 | CH return NTC thermostat fault | View Solution → |
| E50 | DHW NTC thermostat sensor fault | View Solution → |
| E83/84/85/86/87 | No communication | View Solution → |
| E109 | Pre-circulation fault | View Solution → |
| E110 | Boiler max temperature exceeded or safety thermostat | View Solution → |
| E118 | Primary system water pressure too low (<0.5 bar) | View Solution → |
| E125 | Circulation fault (primary) | View Solution → |
| E128 | Frequent flame failure (12 times) | View Solution → |
| E129 | Safety error for frequent loss of flame | View Solution → |
| E130 | Flue thermostat sensor tripped (lockout) | View Solution → |
| E133 | Failure to light – possible gas supply issue | View Solution → |
| E134 | Gas valve open without gas | View Solution → |
| E135 | Interruption of gas supply (internal error) | View Solution → |
| E154 | Flow/return sensor temperature test | View Solution → |
| E160 | Fan or fan wiring fault | View Solution → |
| E163 | DHW NTC thermostat sensor fault | View Solution → |
| E270 | Circulation fault (dry fire) | View Solution → |
| E317 | Wrong power supply electrical frequency (Hz) | View Solution → |
| E321 | Hot water NTC fault | View Solution → |
| E384 | False flame | View Solution → |
| E385 | Under voltage | View Solution → |
| E430 | Water pressure temporary test | View Solution → |
| E430 + Flame | Water pressure test failed | View Solution → |
| LED Pattern | Fault | Solution |
|---|---|---|
| 1 green flash | Boiler temperature reached – normal | No action required |
| 3 green flashes | Temporary flame loss – will self reset | View Solution → |
| 4 green flashes | Communication error – will self reset | View Solution → |
| 5 green flashes | Parameter error on PSU/PCB – will self reset | View Solution → |
| 6 green flashes | Miscellaneous error | View Solution → |
| 1 red flash | Sensor error or temperature fault | View Solution → |
| 2 red flashes | Boiler overheat tripped | View Solution → |
| 3 red flashes | Ignition fault – 5 failed attempts | View Solution → |
| 4 red flashes | Fan fault | View Solution → |
| 5 red flashes | PSU error | View Solution → |
| 6 red flashes | Miscellaneous error | View Solution → |
| Fault Code | Possible Cause | Solution |
|---|---|---|
| E0 | Temperature sensor fault | View Solution → |
| E1 | Overheated – try bleeding radiators | View Solution → |
| E2 | Poor circulation – try bleeding radiators | View Solution → |
| E3 | Printed circuit board (PCB) fault | View Solution → |
| E4 | Ignition failure | View Solution → |
| E10 | Poor/No circulation | View Solution → |
| E12 | Printed circuit board (PCB) fault | View Solution → |
| E13 | Heat exchanger thermal fuse tripped | View Solution → |
| E83/84/85/86/87 | Fan fault (normally E8) | View Solution → |
| Fault Code | Possible Cause | Solution |
|---|---|---|
| E4 | Ignition failure | View Solution → |
| E09 | Gas valve wiring fault | View Solution → |
| E10 | Outdoor sensor error | View Solution → |
| E15 | Gas valve connection fault | View Solution → |
| E20 | Central heating thermistor sensor fault | View Solution → |
| E28 | Flue thermistor fault | View Solution → |
| E40 | Central heating return thermistor fault | View Solution → |
| E53 | Flue obstruction / poor combustion | View Solution → |
| E55 | Calibration required | View Solution → |
| E78 | Water pressure sensor fault | View Solution → |
| E92 | Combustion test alarm during auto-setting | View Solution → |
| E109 | Poor circulation | View Solution → |
| E110 | Boiler overheat tripped | View Solution → |
| E117 | System pressure high (>2.9 bar) | View Solution → |
| E118 | System pressure low (<0.5 bar) | View Solution → |
| E125 | Primary water circulation fault | View Solution → |
| E128 | Loss of flame during operation | View Solution → |
| E129 | Loss of flame during calibration | View Solution → |
| E133 | Ignition fault | View Solution → |
| E135 | Internal error | View Solution → |
| E154 | Primary flow fault | View Solution → |
| E160 | Fan fault | View Solution → |
| E270 | Dry fire | View Solution → |
| E317 | Wrong power supply (Hz) | View Solution → |
| E321 | Hot water thermistor fault | View Solution → |
| E384 | Flame detected when gas valve off | View Solution → |
| E385 | Low voltage (<195V) | View Solution → |
Note: Baxi Solo uses LED combinations. Check your boiler display:
| LED Pattern | Fault | Solution |
|---|---|---|
| FLASH FLASH ON | Fan error | View Solution → |
| FLASH OFF FLASH | Voltage less than 180V | View Solution → |
| FLASH OFF ON | Overheat lockout | View Solution → |
| FLASH ON FLASH | PCB error | View Solution → |
| FLASH ON ON | PCB fault | View Solution → |
| OFF OFF OFF | No power | View Solution → |
| ON FLASH FLASH | Circulation error or dry fire | View Solution → |
| ON FLASH ON | Thermistor error | View Solution → |
| ON OFF FLASH | Live and neutral reversed error | View Solution → |
| ON OFF ON | Ignition lockout error | View Solution → |
| ON ON FLASH | PCB error | View Solution → |
| ON ON ON | Low voltage wiring harness error | View Solution → |
The most common Baxi fault. Usually a simple DIY fix by repressurising your heating system to 1-1.5 bar.
Very common in winter. Often caused by frozen condensate pipe blocking the boiler's drainage system.
Requires professional repair. The fan is critical for safe operation and must be fixed by a Gas Safe engineer.
If you’re seeing E133 or E28 error codes during cold weather, your condensate pipe is almost certainly frozen. This is the #1 cause of Baxi boiler breakdowns in winter.
**Quick Fix:**
Pour warm (NOT boiling) water along the external condensate pipe to thaw it. The pipe is usually white or grey plastic, 21-32mm diameter, running from your boiler to an outside drain.
**Prevention:**
Have your condensate pipe properly insulated by a Gas Safe engineer to prevent future freezing.
Need emergency help? Call us now: 01304 381999
❌ NEVER Attempt DIY:
These faults require Gas Safe registered engineers with specialised diagnostic equipment.
✅ You CAN Try:
Important: If the fault returns after your fix, call a professional. Repeated faults indicate an underlying problem.
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