Baxi boilers show an E followed by three numbers. Some displays alternate between two parts, so E133 can appear as E1 then 33. These codes apply to most Baxi boilers; the newer Baxi Combi 2 and System 2 ranges use different codes.
E133 is by far the most common Baxi code. Baxi says it points to the gas supply, the ignition, or a blocked or frozen condensate pipe.
| Code | What it means | Models | Can you fix it? |
|---|---|---|---|
| E133 | Gas supply or ignition fault. | Platinum, Duo-tec, EcoBlue, Megaflo, Assure, Main Eco and original 600/800 | Checks first |
| E118 | Low water pressure (below 0.5 bar). | Platinum, Duo-tec, EcoBlue, Megaflo, Assure, Main Eco and original 600/800 | Usually yes |
| E110 | Overheat: the safety thermostat has tripped. | Platinum, Duo-tec, EcoBlue, Megaflo, Assure, Main Eco and original 600/800 | No, engineer only |
| E125 | Water circulation fault. | Platinum, Duo-tec, EcoBlue, Megaflo, Assure, Main Eco and original 600/800 | No, engineer only |
| E160 | Fan fault. | Platinum, Duo-tec, EcoBlue, Megaflo, Assure, Main Eco and original 600/800 | No, engineer only |
| A.00.28 | Solar temperature sensor removed, or measuring below range. | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| A.00.29 | Solar temperature sensor shorted, or measuring above range. | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| A.00.34 | Outdoor temperature sensor expected but not detected. | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| A.02.06 | Low system pressure in heating circuit. | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | Usually yes |
| A.02.18 | OBD error. | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| A.02.36 | Functional device disconnected. | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| A.02.37 | Passive functional device disconnected. | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| A.02.45 | Connection error. | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| A.02.46 | Device priority error. | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| A.02.48 | Unit function configuration error. | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| A.02.49 | Failed node initialisation. | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| A.02.54 | OpenTherm bus power supply error. | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| A.02.55 | Incorrect or missing serial number. | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| A.02.76 | Internal memory for custom settings is full; no further changes can be made. | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| E.00.04 | Return temperature sensor disconnected. | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| E.00.05 | Return temperature sensor short circuited. | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| E09 | Gas valve connection fault. | Platinum, Duo-tec, EcoBlue, Megaflo, Assure, Main Eco and original 600/800 | No, engineer only |
| E10 | External probe fault. | Platinum, Duo-tec, EcoBlue, Megaflo, Assure, Main Eco and original 600/800 | No, engineer only |
| E12 | Differential water flow switch fault (still open). | Platinum, Duo-tec, EcoBlue, Megaflo, Assure, Main Eco and original 600/800 | No, engineer only |
| E13 | Differential water flow switch fault (still closed). | Platinum, Duo-tec, EcoBlue, Megaflo, Assure, Main Eco and original 600/800 | No, engineer only |
| E15 | Gas valve command fault. | Platinum, Duo-tec, EcoBlue, Megaflo, Assure, Main Eco and original 600/800 | No, engineer only |
| E.00.16 | Hot water tank temperature sensor not connected. | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| E.00.17 | Hot water tank temperature sensor short-circuited. | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| E20 | Central heating temperature sensor fault: short circuit or open circuit. | Platinum, Duo-tec, EcoBlue, Megaflo, Assure, Main Eco and original 600/800 | No, engineer only |
| E.00.20 | Flue gas temperature sensor not connected, or measuring below range. | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| E.00.21 | Flue gas temperature sensor short-circuited, or measuring above range. | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| E28 | Flue temperature sensor fault: short circuit or open circuit. | Platinum, Duo-tec, EcoBlue, Megaflo, Assure, Main Eco and original 600/800 | No, engineer only |
| E40 | Return central heating temperature sensor fault: short circuit or open circuit. | Platinum, Duo-tec, EcoBlue, Megaflo, Assure, Main Eco and original 600/800 | No, engineer only |
| E50 | Hot water temperature sensor fault (tank boiler): short circuit or open circuit. | Platinum, Duo-tec, EcoBlue, Megaflo, Assure, Main Eco and original 600/800 | No, engineer only |
| E83 | No communication. | Platinum, Duo-tec, EcoBlue, Megaflo, Assure, Main Eco and original 600/800 | No, engineer only |
| E84 | No communication. | Platinum, Duo-tec, EcoBlue, Megaflo, Assure, Main Eco and original 600/800 | No, engineer only |
| E85 | No communication. | Platinum, Duo-tec, EcoBlue, Megaflo, Assure, Main Eco and original 600/800 | No, engineer only |
| E86 | No communication. | Platinum, Duo-tec, EcoBlue, Megaflo, Assure, Main Eco and original 600/800 | No, engineer only |
| E87 | No communication. | Platinum, Duo-tec, EcoBlue, Megaflo, Assure, Main Eco and original 600/800 | No, engineer only |
| E103 | Safety Assist battery is exhausted. | Platinum, Duo-tec, EcoBlue, Megaflo, Assure, Main Eco and original 600/800 | No, engineer only |
| E104 | Faulty Safety Assist PCB. | Platinum, Duo-tec, EcoBlue, Megaflo, Assure, Main Eco and original 600/800 | No, engineer only |
| E.01.04 | Flame loss detected five times in 24 hours. | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| E107 | PCBs not synchronised. | Platinum, Duo-tec, EcoBlue, Megaflo, Assure, Main Eco and original 600/800 | No, engineer only |
| E109 | Precirculation alarm. | Platinum, Duo-tec, EcoBlue, Megaflo, Assure, Main Eco and original 600/800 | No, engineer only |
| E.01.12 | Return temperature higher than flow temperature. | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| E.01.17 | No water circulation (permanent). | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| E.01.20 | Maximum flue gas temperature reached. | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| E128 | Safety error for frequent loss of flame. | Platinum, Duo-tec, EcoBlue, Megaflo, Assure, Main Eco and original 600/800 | No, engineer only |
| E129 | Safety error for frequent loss of flame with maximum correction during ignition. | Platinum, Duo-tec, EcoBlue, Megaflo, Assure, Main Eco and original 600/800 | No, engineer only |
| E130 | Flue thermostat sensor tripped (lockout). | Platinum, Duo-tec, EcoBlue, Megaflo, Assure, Main Eco and original 600/800 | No, engineer only |
| E134 | Gas valve open for too long without gas. | Platinum, Duo-tec, EcoBlue, Megaflo, Assure, Main Eco and original 600/800 | No, engineer only |
| E135 | Internal error. | Platinum, Duo-tec, EcoBlue, Megaflo, Assure, Main Eco and original 600/800 | No, engineer only |
| E154 | Plausibility test (flow/return). | Platinum, Duo-tec, EcoBlue, Megaflo, Assure, Main Eco and original 600/800 | No, engineer only |
| E.02.13 | Total stoppage of the boiler (antifreeze function not active). | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| E.02.17 | Permanent communication failure between gas valve and boiler PCB. | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| E.02.35 | Critical safety device disconnected. | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| E.02.39 | Minimum pressure not reached after 6 minutes of automatic filling. | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| E.02.47 | Connection to external device unsuccessful. | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| E270 | Dry fire. | Platinum, Duo-tec, EcoBlue, Megaflo, Assure, Main Eco and original 600/800 | No, engineer only |
| E317 | Wrong power supply electrical frequency (Hz) (also shown as 162). | Platinum, Duo-tec, EcoBlue, Megaflo, Assure, Main Eco and original 600/800 | No, engineer only |
| E321 | Hot water temperature sensor fault (also shown as 163). | Platinum, Duo-tec, EcoBlue, Megaflo, Assure, Main Eco and original 600/800 | No, engineer only |
| E384 | False flame (parasitic flame) (also shown as 164). | Platinum, Duo-tec, EcoBlue, Megaflo, Assure, Main Eco and original 600/800 | No, engineer only |
| E385 | Under voltage (also shown as 165). | Platinum, Duo-tec, EcoBlue, Megaflo, Assure, Main Eco and original 600/800 | No, engineer only |
| E.04.01 | Flow temperature sensor short circuited. | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| E.04.02 | Flow temperature sensor disconnected. | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| E.04.03 | Maximum flow temperature exceeded, or flow temperature sensor short circuited. | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| E.04.08 | Maximum safe temperature reached. | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| E.04.10 | Burner failed to ignite after 4 attempts. | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| E.04.12 | Ignition failure (flame monitoring). | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| E.04.13 | Fan impeller blocked or maximum rpm exceeded. | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| E.04.17 | Fault in gas valve control circuit. | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| E.04.18 | Flow temperature below minimum, or flow temperature sensor not connected. | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| E.04.23 | Internal communication stoppage. | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| E.04.29 | Internal communication stoppage. | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| E430 | Water pressure temporary fault or test failed (also shown as 166). | Platinum, Duo-tec, EcoBlue, Megaflo, Assure, Main Eco and original 600/800 | No, engineer only |
| E.04.54 | Fault in gas valve control circuit. | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| E.04.254 | Fault in gas valve control circuit. | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| H.00.42 | Pressure sensor open or faulty. | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| H.00.81 | Room unit disconnected. | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| H.01.00 | Temporary communication failure between gas valve and boiler PCB. | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| H.01.05 | Maximum temperature difference between flow and return reached. | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| H.01.08 | Flow temperature rising too quickly in heating mode (10-minute temporary stop). | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| H.01.14 | Maximum flow or return temperature reached. | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| H.01.18 | No water circulation (temporary). | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| H.01.21 | Flow temperature rising too fast during hot water operation. | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| H.02.02 | Waiting for configuration settings to be entered (CN1, CN2). | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| H.02.03 | Configuration settings (CN1, CN2) not entered correctly. | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| H.02.04 | PCB settings cannot be read. | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| H.02.05 | Setting memory not compatible with the boiler PCB type. | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| H.02.07 | Low pressure in heating circuit (permanent). | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | Usually yes |
| H.02.09 | Partial stoppage of the boiler (antifreeze function active). | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| H.02.10 | Total stoppage of the boiler (antifreeze function not active). | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| H.02.70 | External unit heat recovery test failed. | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| H.03.00 | No identification data for boiler safety device. | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| H.03.02 | Temporary flame loss. | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| H.03.05 | Power supply voltage too low. | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |
| H.03.54 | Temporary flame loss: shutdown because the power supply voltage is too low. | Baxi Combi 2 and System 2 (200, 400, 600, 800, Assure 500) | No, engineer only |