Baxi 600 Combi and 600 System fault codes
Built 2018–2023
Compact cupboard-fit combi (624, 630, 636) and system boiler. Digital display, Reset button held one to three seconds. The installation manual carries the fault-finding flowcharts most of the engineer-side detail on these pages comes from, and a short parts list with Baxi part numbers.
Codes on the 600 Combi and 600 System follow the same Baxi scheme as the rest of the range. Where a code behaves differently on this generation, the code page says so.
Baxi fault codes
Every published Baxi code. Open a code to see which models and years it applies to.
- E133Baxi's ignition lockout: "the gas supply has been interrupted, ignition has failed or the flame has not been detected". Check the gas is on, reset once. If it returns, stop.Get it checked
- E118Low water pressure on the digital-display Baxis: 600, 800, Duo-tec 2, Compact, Assure, Megaflo. Defined by Baxi as primary pressure under 0.5 bar. Repressurise and it clears itself.Get it checked
- E119Low water pressure on the selector-switch Baxis — Duo-tec Combi HE, Platinum, Megaflo System HE A. Shown as E1 then 19. Repressurise; no reset is needed.Get it checked
- E.04.10Ignition failure on the Baxi 200/400 Combi and every Combi 2: the burner would not light after its allowed attempts. Baxi's own quick guide names it the frozen-condensate code you can fix yourself.Get it checked
- E.02.07Low water pressure made permanent on the Baxi 200/400 Combi and Combi 2, after A.02.06 or H.02.06 has been showing. Repressurise to 1 to 1.5 bar and reset; Baxi say you can do it yourself.Usually simple to fix
- E110The safety thermostat has tripped on overheat — "overheat of the primary water" in Baxi's words. One reset is allowed on every generation. If it trips again, the water is not moving.Stop — call an engineer
- E125Baxi's primary circulation fault, decided by two temperature tests the manuals spell out. Pump, air or a blocked filter; the pressure is usually fine.Get it checked
- E128Flame failure while the burner was running, on the digital-display Baxis. The boiler relights itself unless it keeps happening; Baxi's manuals name gas supply, electrode and flue as the things to check.Get it checked
- E130"Flue NTC operated": the flue gas got too hot and the boiler shut down. Baxi allow one reset on every generation, then it is a heat exchanger or flue problem for an engineer.Stop — call an engineer
- E160Fan fault on every three-digit Baxi. The boiler will not light without proof the fan is moving combustion air. No householder reset on any generation; fan, wiring or board.Stop — call an engineer
- E28Flue thermistor fault — and on the Platinum ranges also the air pressure switch, a blocked flue or a blocked condensate drain. Which meaning applies depends on which Baxi you have.Get it checked
- E.04.08"Maximum safe temperature value reached": the safety thermostat has opened on a Baxi 200/400 Combi or Combi 2. Circulation first, the thermostat second, in Baxi's own order. One reset, then an engineer.Stop — call an engineer
- E134Baxi's "elapsed time — gas valve open without gas": the valve opened, nothing arrived. Check the meter and credit before anything else; it resets from the panel.Get it checked
- E.01.17"No water circulation (permanent)" on the Baxi 200/400 Combi and Combi 2, after H.01.18 has shown as a temporary block. Pressure, venting and the pump, in Baxi's order; reset once.Get it checked
- E.01.04"Flame loss detected five times in 24 hours": the burner keeps lighting and going out on a Baxi 200/400 Combi or Combi 2. Gas pressure, valve calibration, flue or electrode — an engineer's list.Stop — call an engineer
- E109Pre-circulation fault on the digital-display Baxis: the board could not confirm water moving before it would light the burner. Vent the system; Baxi allow a reset from the button.Get it checked
- E117Primary water pressure too high, on the Duo-tec 2 and EcoBlue Advance. Usually an overfilled system or a flat expansion vessel. Let some water out and it clears.Get it checked
- E09Gas valve connection cable fault on the 600, 800, Compact and Duo-tec 2. The board cannot talk to the valve. Baxi allow one reset; a repeat means the wiring or the PCB.Get it checked
- E20Central heating flow thermistor open or short circuit. Baxi list E20 as a faulty component on every generation, with no householder reset; a cheap sensor swap for an engineer.Get it checked
- E.04.13Fan blocked or over speed on the Baxi 200/400 Combi and Combi 2. Baxi's remedy is the fan-and-PCB connection, then the air-gas unit. No householder fix; do not keep resetting.Stop — call an engineer
- E135Baxi's "interruption of gas supply (internal error)". Same family as E133 and E134 but the manual calls it internal, so a reset that fails means the board or gas valve circuit.Get it checked
- E384False flame: the board sees a flame signal when the burner should be off. Baxi's manuals point at the electrode, its lead and the PCB. Resettable, but not a fault to live with.Get it checked
- E15Gas valve fault on the digital-display Baxis — "gas valve command fault" on Baxi's professional page. One reset is allowed; after that it is the valve or the board.Get it checked
- E270Baxi's dry-fire circulation fault: the heat exchanger was heating with too little water passing through it. Air, a stopped pump or a closed circuit; not a code to reset repeatedly.Get it checked
- E.04.01Flow temperature sensor short circuit (E.04.01) or disconnected (E.04.02) on the Baxi 200/400 Combi and Combi 2. A sensor or its plug; Baxi's remedy is check the connection, then the sensor.Get it checked
- E.04.17Gas valve control circuit fault on the Baxi 200/400 Combi and Combi 2. Baxi's remedy is the main PCB or the air-gas unit, and there is nothing for the householder to try.Stop — call an engineer
- E154Flow and return sensor temperature test failed — the two readings do not make sense together. Usually a sensor or its plug, sometimes poor circulation. Engineer diagnosis.Get it checked
- E168Trade lists call E168 a Baxi PCB lockout, but no Baxi UK manual or error-code page prints it. Treat it as a board fault: one power cycle, then an engineer.Get it checked
- E193Pre-circulation fault on the selector-switch Baxis (Duo-tec Combi HE, Platinum, Megaflo HE A), shown as E1 then 93. Baxi offer no reset for it; the pump or air is the cause.Get it checked
- E40Return thermistor open or short circuit on the digital-display Baxis. Spanner symbol, no householder reset, and the same inexpensive sensor as the flow side.Get it checked
- E430A temporary water-pressure fault on the 600, 800 and Compact family, from Baxi's professional error-code table. If it comes with a crossed flame symbol the pressure self-test has failed.Get it checked
- E.01.20"Maximum flue gas temperature reached" on the Baxi 200/400 Combi and Combi 2. Baxi's cause is a heat exchanger blocked on the flue side; the fix is a strip and clean, not a reset.Stop — call an engineer
- E50Hot water thermistor fault on the selector-switch Baxis, shown as E then 50. Heating usually carries on; hot water is unreliable until the sensor is changed. Digital-display combis show E321 instead.Usually simple to fix
- E83E83 to E87: the boiler has lost contact with a connected control — a room unit or programmer wired to the board. Check the control first; the boiler itself is usually fine.Usually simple to fix
- E321Domestic hot water thermistor fault on the digital-display Baxis (shown on some as 163). Heating normally continues; tap temperature control is lost until the sensor is replaced.Usually simple to fix
- E.04.12False flame signal on the Baxi 200/400 Combi and Combi 2: the board sees a flame with the gas off. Electrode, earthing or a very hot burner; the 200/400 manual asks for a five-second reset.Get it checked
- E103Safety Assist codes E103, E104 and E107: the battery-backed safety board on the 600 and 800 is exhausted, faulty or out of step with the main board. Contact your installer; there is no reset.Get it checked
- E.02.47"Connection to external device unsuccessful": a Baxi 200/400 Combi or Combi 2 has lost a control it was paired with. Check the control and its wiring; Baxi's remedy is the auto-detect function.Usually simple to fix
- E55"Calibration Required": the gas valve has not been set up to the board after a PCB or valve change. An engineer's combustion-analyser job, not a fault a householder can clear.Get it checked
- E317Mains frequency out of range (shown on some boards as 162). The boiler, not the supply, is almost always the odd one out. Check other appliances, then call an engineer.Get it checked
- E385Under-voltage (shown on some boards as 165): the supply at the board dropped below what it will run on. Usually a house-wiring or supply problem the boiler is reporting, not causing.Get it checked
- H.02.09Not a fault: a Baxi Combi 2 or 200/400 Combi has been told to stop by an external input, or frost protection is running. Baxi's remedy is to find and remove the external cause.Usually simple to fix
- H.03.05"Power supply voltage too low" on a Baxi Combi 2: the boiler pauses until the mains recovers and clears itself. Baxi's only remedy is to check the mains voltage; if it recurs, an electrician.Get it checked
Other Baxi models
- 200 Combi and 400 Combi
- 200, 400, 600 and 800 Combi 2, 600 and 800 System 2, Assure 500
- 200, 400, 600 and 800 Heat, Assure Heat, EcoBlue Advance Heat
- 800 Combi and 800 System
- Assure Combi and Assure System
- Bermuda back boiler units
- Combi 80e, 105e and Combi Instant 80e, 105e, 80 HE, 105 HE
- Duo-tec 2 Combi GA, Duo-tec Compact, Platinum Compact, Megaflo Compact
- Duo-tec Combi HE and HE A
- Megaflo System HE A, Megaflo System GA and Megaflo System
- Platinum Combi HE, Platinum+ 40 Combi and Platinum+ 32 System
- Solo HE and Solo HE A