Common questions about Baxi codes · Search all brands by code or symptom
What is safe for you to do
Every code here follows the same safety rules. You can:
- press the reset button once, as your user guide shows;
- for low-pressure codes, top up the pressure with the filling loop, as your user guide shows;
- for ignition and flame-loss codes, check the gas is on at the meter and a prepayment meter has credit;
- thaw a frozen plastic condensate pipe outside with warm (not boiling) water;
- check the thermostat, timer and power to the boiler.
Never open the boiler casing. Only a Gas Safe registered engineer may work inside a gas boiler. Codes marked Engineer after one reset have no homeowner fix: reset once, then leave them to an engineer. Codes marked Safe checks first list the one check that relates to that code.
Baxi 600 Combi 2 (24 / 30 / 36)
The 600 Combi 2 shows a letter, a group number and a specific number, e.g. E.04.10. H codes are temporary (the boiler restarts itself when the cause clears); E codes are permanent and need a reset; A codes are warnings.
Source: Baxi 600 Combi 2 Installation and Service Manual & Boiler Fiche, doc. 7796561-03 (04/23), pp. 73–77, section 11.2 Error codes (Tab. 33 and Tab. 34). Open the manual (PDF) (Manufacturer copy)
Ignition / flame
H.03.02 Baxi 600 Combi 2
Safe checks firstIgnition / flameWhat it means
The flame was lost temporarily.
Likely causes
Electrode wiring or condition, low gas supply pressure, gas valve calibration, or a flue/terminal problem.
What you can safely do
Check another gas appliance such as the hob works, the gas meter valve is on and, on a prepayment meter, there is credit. In freezing weather, check the plastic condensate pipe outside: if it is frozen, pour warm (not boiling) water along it. Then press reset once. If the code comes back, stop resetting.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if the gas supply is fine and the code returns after one reset. Ignition and flame faults involve gas, so this is engineer-only.
What does H.03.02 mean on a Baxi 600 Combi 2 boiler?
On a Baxi 600 Combi 2, H.03.02 means the flame was lost temporarily. Likely causes include electrode wiring or condition, low gas supply pressure, gas valve calibration, or a flue/terminal problem. Check another gas appliance works, the meter valve is on and any prepay meter has credit, then reset once. If it returns, book a Gas Safe registered engineer.
H.03.54 Baxi 600 Combi 2
Safe checks firstIgnition / flameWhat it means
Temporary flame loss, or shutdown because the supply voltage is too low.
Likely causes
Electrode problems, low gas inlet pressure, gas valve calibration, the air intake or flue terminal, or low mains voltage.
What you can safely do
Check another gas appliance such as the hob works, the gas meter valve is on and, on a prepayment meter, there is credit. In freezing weather, check the plastic condensate pipe outside: if it is frozen, pour warm (not boiling) water along it. Then press reset once. If the code comes back, stop resetting.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if the gas supply is fine and the code returns after one reset. Ignition and flame faults involve gas, so this is engineer-only.
What does H.03.54 mean on a Baxi 600 Combi 2 boiler?
On a Baxi 600 Combi 2, H.03.54 is listed in the manufacturer's table as "Temporary flame loss, or shutdown because the supply voltage is too low". Check another gas appliance works, the meter valve is on and any prepay meter has credit, then reset once. If it returns, book a Gas Safe registered engineer.
E.01.04 Baxi 600 Combi 2
Safe checks firstIgnition / flameWhat it means
The flame was lost five times in 24 hours with the burner on, so the boiler locked out.
Likely causes
Low gas supply pressure, gas valve calibration, the air intake or flue terminal, or the power supply voltage.
What you can safely do
Check another gas appliance such as the hob works, the gas meter valve is on and, on a prepayment meter, there is credit. In freezing weather, check the plastic condensate pipe outside: if it is frozen, pour warm (not boiling) water along it. Then press reset once. If the code comes back, stop resetting.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if the gas supply is fine and the code returns after one reset. Ignition and flame faults involve gas, so this is engineer-only.
What does E.01.04 mean on a Baxi 600 Combi 2 boiler?
On a Baxi 600 Combi 2, E.01.04 means the flame was lost five times in 24 hours with the burner on, so the boiler locked out. Check another gas appliance works, the meter valve is on and any prepay meter has credit, then reset once. If it returns, book a Gas Safe registered engineer.
E.04.10 Baxi 600 Combi 2
Safe checks firstIgnition / flameWhat it means
The burner failed to light after four attempts. This is the 600 Combi 2's ignition lockout.
Likely causes
Gas supply pressure, gas valve wiring, calibration or operation, the electrode or its wiring, the fan, or a blocked flue.
What you can safely do
Check another gas appliance such as the hob works, the gas meter valve is on and, on a prepayment meter, there is credit. In freezing weather, check the plastic condensate pipe outside: if it is frozen, pour warm (not boiling) water along it. Then press reset once. If the code comes back, stop resetting.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if the gas supply is fine and the code returns after one reset. Ignition and flame faults involve gas, so this is engineer-only.
What does E.04.10 mean on a Baxi 600 Combi 2 boiler?
On a Baxi 600 Combi 2, E.04.10 means the burner failed to light after four attempts. This is the 600 Combi 2's ignition lockout. Check another gas appliance works, the meter valve is on and any prepay meter has credit, then reset once. If it returns, book a Gas Safe registered engineer.
E.04.12 Baxi 600 Combi 2
Engineer after one resetIgnition / flameWhat it means
Ignition failure while checking for a parasitic (false) flame.
Likely causes
An earthing (ground circuit) fault or the power supply voltage.
What you can safely do
There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if the code comes back after one reset. Ignition and flame faults involve gas, so this is engineer-only.
What does E.04.12 mean on a Baxi 600 Combi 2 boiler?
On a Baxi 600 Combi 2, E.04.12 is listed in the manufacturer's table as "Ignition failure while checking for a parasitic (false) flame". There is no homeowner fix for this. You can reset once, but do not open the casing; book a Gas Safe registered engineer and quote the full code.
E.04.17 Baxi 600 Combi 2
Engineer after one resetIgnition / flameWhat it means
Fault in the gas valve control circuit.
Likely causes
Main board fault.
What you can safely do
There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if the code comes back after one reset. Ignition and flame faults involve gas, so this is engineer-only.
What does E.04.17 mean on a Baxi 600 Combi 2 boiler?
On a Baxi 600 Combi 2, E.04.17 is listed in the manufacturer's table as "Fault in the gas valve control circuit". Likely causes include main board fault. There is no homeowner fix for this. You can reset once, but do not open the casing; book a Gas Safe registered engineer and quote the full code.
E.04.54 Baxi 600 Combi 2
Engineer after one resetIgnition / flameWhat it means
Fault in the gas valve control circuit.
Likely causes
Gas valve wiring, the gas valve or the board.
What you can safely do
There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if the code comes back after one reset. Ignition and flame faults involve gas, so this is engineer-only.
What does E.04.54 mean on a Baxi 600 Combi 2 boiler?
On a Baxi 600 Combi 2, E.04.54 is listed in the manufacturer's table as "Fault in the gas valve control circuit". There is no homeowner fix for this. You can reset once, but do not open the casing; book a Gas Safe registered engineer and quote the full code.
Water pressure / circulation
A.02.06 Baxi 600 Combi 2
Safe checks firstWater pressure / circulationWhat it means
Warning: water pressure in the heating system is low.
Likely causes
Water lost from the system (leaks, bleeding radiators, the pressure relief valve) or an expansion vessel that has lost its charge.
What you can safely do
Look at the pressure gauge while the boiler is cold. If it is below about 1 bar, top it up with the filling loop exactly as your user guide shows, to about 1–1.5 bar or the figure in your guide, then close the loop fully. Check the radiator valves are open, then press reset once.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if you have to top up more than once every few months, the gauge goes above about 2.5 bar when hot, water drips from the outside overflow pipe, or the code returns after topping up.
What does A.02.06 mean on a Baxi 600 Combi 2 boiler?
On a Baxi 600 Combi 2, A.02.06 is a warning: water pressure in the heating system is low. With the boiler cold, check the pressure gauge; if it is below the level in your user guide, top it up as the guide shows, then reset once. If it returns, book a Gas Safe registered engineer.
H.00.42 Baxi 600 Combi 2
Engineer after one resetWater pressure / circulationWhat it means
The pressure sensor is open circuit or faulty (shown while a reset is in progress).
Likely causes
Pressure sensor or its connection.
What you can safely do
Look at the pressure gauge while the boiler is cold. If it is below about 1 bar, top it up with the filling loop exactly as your user guide shows, to about 1–1.5 bar or the figure in your guide, then close the loop fully. Check the radiator valves are open, then press reset once.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if you have to top up more than once every few months, the gauge goes above about 2.5 bar when hot, water drips from the outside overflow pipe, or the code returns after topping up.
What does H.00.42 mean on a Baxi 600 Combi 2 boiler?
On a Baxi 600 Combi 2, H.00.42 means the pressure sensor is open circuit or faulty (shown while a reset is in progress). Likely causes include pressure sensor or its connection. Reset once; if the code comes back, book a Gas Safe registered engineer and quote the full code. Do not open the casing.
H.01.05 Baxi 600 Combi 2
Engineer after one resetWater pressure / circulationWhat it means
The temperature difference between flow and return has reached its maximum.
Likely causes
Poor circulation, low pressure, air in the system, a dirty heat exchanger or a temperature sensor problem.
What you can safely do
There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if you have to top up more than once every few months, the gauge goes above about 2.5 bar when hot, water drips from the outside overflow pipe, or the code returns after topping up.
What does H.01.05 mean on a Baxi 600 Combi 2 boiler?
On a Baxi 600 Combi 2, H.01.05 means the temperature difference between flow and return has reached its maximum. Reset once; if the code comes back, book a Gas Safe registered engineer and quote the full code. Do not open the casing.
H.01.18 Baxi 600 Combi 2
Engineer after one resetWater pressure / circulationWhat it means
No water circulation was detected (temporary).
Likely causes
Low pressure, air, a pump not running, closed valves, or a temperature sensor fault.
What you can safely do
There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if you have to top up more than once every few months, the gauge goes above about 2.5 bar when hot, water drips from the outside overflow pipe, or the code returns after topping up.
What does H.01.18 mean on a Baxi 600 Combi 2 boiler?
On a Baxi 600 Combi 2, H.01.18 means no water circulation was detected (temporary). Likely causes include low pressure, air, a pump not running, closed valves, or a temperature sensor fault. Reset once; if the code comes back, book a Gas Safe registered engineer and quote the full code. Do not open the casing.
H.02.07 Baxi 600 Combi 2
Safe checks firstWater pressure / circulationWhat it means
Pressure in the heating circuit is low (the boiler stops until it is restored).
Likely causes
Water loss from leaks or the pressure relief valve, or an expansion vessel that has lost its charge.
What you can safely do
Look at the pressure gauge while the boiler is cold. If it is below about 1 bar, top it up with the filling loop exactly as your user guide shows, to about 1–1.5 bar or the figure in your guide, then close the loop fully. Check the radiator valves are open, then press reset once.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if you have to top up more than once every few months, the gauge goes above about 2.5 bar when hot, water drips from the outside overflow pipe, or the code returns after topping up.
What does H.02.07 mean on a Baxi 600 Combi 2 boiler?
On a Baxi 600 Combi 2, H.02.07 means the pressure in the heating circuit is low (the boiler stops until it is restored). With the boiler cold, check the pressure gauge; if it is below the level in your user guide, top it up as the guide shows, then reset once. If it returns, book a Gas Safe registered engineer.
E.01.17 Baxi 600 Combi 2
Engineer after one resetWater pressure / circulationWhat it means
No water circulation (permanent lockout).
Likely causes
Low pressure, air, a pump not working, poor circulation, or a temperature sensor fault.
What you can safely do
There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if you have to top up more than once every few months, the gauge goes above about 2.5 bar when hot, water drips from the outside overflow pipe, or the code returns after topping up.
What does E.01.17 mean on a Baxi 600 Combi 2 boiler?
On a Baxi 600 Combi 2, E.01.17 is listed in the manufacturer's table as "No water circulation (permanent lockout)". Likely causes include low pressure, air, a pump not working, poor circulation, or a temperature sensor fault. Reset once; if the code comes back, book a Gas Safe registered engineer and quote the full code. Do not open the casing.
Temperature / overheat
H.01.08 Baxi 600 Combi 2
Engineer after one resetTemperature / overheatWhat it means
The heating flow temperature rose too quickly; the boiler pauses for 10 minutes.
Likely causes
Poor circulation, low pressure, air, a dirty heat exchanger or a sensor problem.
What you can safely do
Let the boiler cool for 20 to 30 minutes, then press reset once. If the code comes back, leave the boiler off.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if the code comes back after one reset. Overheat shut-downs are safety devices doing their job, so this is engineer-only.
What does H.01.08 mean on a Baxi 600 Combi 2 boiler?
On a Baxi 600 Combi 2, H.01.08 is listed in the manufacturer's table as "The heating flow temperature rose too quickly; the boiler pauses for 10 minutes". There is no homeowner fix for this. You can reset once, but do not open the casing; book a Gas Safe registered engineer and quote the full code.
H.01.14 Baxi 600 Combi 2
Engineer after one resetTemperature / overheatWhat it means
The maximum flow temperature has been reached.
Likely causes
Poor circulation through the boiler or system, or air in the system.
What you can safely do
Let the boiler cool for 20 to 30 minutes, then press reset once. If the code comes back, leave the boiler off.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if the code comes back after one reset. Overheat shut-downs are safety devices doing their job, so this is engineer-only.
What does H.01.14 mean on a Baxi 600 Combi 2 boiler?
On a Baxi 600 Combi 2, H.01.14 means the maximum flow temperature has been reached. Likely causes include poor circulation through the boiler or system, or air in the system. There is no homeowner fix for this. You can reset once, but do not open the casing; book a Gas Safe registered engineer and quote the full code.
H.01.21 Baxi 600 Combi 2
Engineer after one resetTemperature / overheatWhat it means
The flow temperature rose too quickly in hot water mode; the boiler pauses for 10 minutes.
Likely causes
Low pressure, air, the pump, poor circulation or a sensor fault.
What you can safely do
Let the boiler cool for 20 to 30 minutes, then press reset once. If the code comes back, leave the boiler off.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if the code comes back after one reset. Overheat shut-downs are safety devices doing their job, so this is engineer-only.
What does H.01.21 mean on a Baxi 600 Combi 2 boiler?
On a Baxi 600 Combi 2, H.01.21 is listed in the manufacturer's table as "The flow temperature rose too quickly in hot water mode; the boiler pauses for 10 minutes". There is no homeowner fix for this. You can reset once, but do not open the casing; book a Gas Safe registered engineer and quote the full code.
E.04.03 Baxi 600 Combi 2
Engineer after one resetTemperature / overheatWhat it means
The maximum flow temperature has been exceeded.
Likely causes
Poor circulation, air in the system or a sensor fault.
What you can safely do
Let the boiler cool for 20 to 30 minutes, then press reset once. If the code comes back, leave the boiler off.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if the code comes back after one reset. Overheat shut-downs are safety devices doing their job, so this is engineer-only.
What does E.04.03 mean on a Baxi 600 Combi 2 boiler?
On a Baxi 600 Combi 2, E.04.03 means the maximum flow temperature has been exceeded. Likely causes include poor circulation, air in the system or a sensor fault. There is no homeowner fix for this. You can reset once, but do not open the casing; book a Gas Safe registered engineer and quote the full code.
E.04.08 Baxi 600 Combi 2
Engineer after one resetTemperature / overheatWhat it means
The maximum safe temperature has been reached (the safety thermostat has acted).
Likely causes
Low pressure, air, the pump, poor circulation, or the safety thermostat or its connection.
What you can safely do
Let the boiler cool for 20 to 30 minutes, then press reset once. If the code comes back, leave the boiler off.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if the code comes back after one reset. Overheat shut-downs are safety devices doing their job, so this is engineer-only.
What does E.04.08 mean on a Baxi 600 Combi 2 boiler?
On a Baxi 600 Combi 2, E.04.08 means the maximum safe temperature has been reached (the safety thermostat has acted). There is no homeowner fix for this. You can reset once, but do not open the casing; book a Gas Safe registered engineer and quote the full code.
Flue / fan / air
E.01.20 Baxi 600 Combi 2
Engineer after one resetFlue / fan / airWhat it means
The maximum flue gas temperature has been reached.
Likely causes
A heat exchanger blocked on the flue gas side.
What you can safely do
There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if the terminal looks clear and the code returns. Flue and fan faults can affect how combustion gases leave your home, so this is engineer-only.
What does E.01.20 mean on a Baxi 600 Combi 2 boiler?
On a Baxi 600 Combi 2, E.01.20 means the maximum flue gas temperature has been reached. Likely causes include a heat exchanger blocked on the flue gas side. There is no homeowner fix for this. You can reset once, but do not open the casing; book a Gas Safe registered engineer and quote the full code.
E.04.13 Baxi 600 Combi 2
Engineer after one resetFlue / fan / airWhat it means
The fan blade is blocked.
Likely causes
Fan-to-board connection or the air/gas unit, which the manual says to replace.
What you can safely do
There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if the terminal looks clear and the code returns. Flue and fan faults can affect how combustion gases leave your home, so this is engineer-only.
What does E.04.13 mean on a Baxi 600 Combi 2 boiler?
On a Baxi 600 Combi 2, E.04.13 means the fan blade is blocked. Likely causes include fan-to-board connection or the air/gas unit, which the manual says to replace. There is no homeowner fix for this. You can reset once, but do not open the casing; book a Gas Safe registered engineer and quote the full code.
E.04.15 Baxi 600 Combi 2
Safe checks firstFlue / fan / airWhat it means
The flue gas exhaust pipe is blocked.
Likely causes
A blockage in the flue or terminal.
What you can safely do
From outside, look at the flue terminal without touching it and make sure nothing is covering it, such as a bag, snow, a nest or stored items. In freezing weather, check the condensate pipe and thaw it with warm (not boiling) water. Press reset once. Do not touch or adjust any flue parts.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if the terminal looks clear and the code returns. Flue and fan faults can affect how combustion gases leave your home, so this is engineer-only.
What does E.04.15 mean on a Baxi 600 Combi 2 boiler?
On a Baxi 600 Combi 2, E.04.15 means the flue gas exhaust pipe is blocked. Likely causes include a blockage in the flue or terminal. From outside, check the flue terminal is not blocked by leaves, a nest or snow, without touching it, then reset once. If it returns, book a Gas Safe registered engineer.
Sensors / thermistors
A.00.34 Baxi 600 Combi 2
Engineer after one resetSensors / thermistorsWhat it means
The boiler expects an outdoor sensor but cannot detect one.
Likely causes
Outdoor sensor not connected or wired incorrectly.
What you can safely do
Nothing urgent: the boiler normally keeps heating without the outdoor sensor, using a fixed setting. Press reset once to see if it clears.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if the code returns. Testing and replacing sensors means opening the casing, so this is engineer-only.
What does A.00.34 mean on a Baxi 600 Combi 2 boiler?
On a Baxi 600 Combi 2, A.00.34 means the boiler expects an outdoor sensor but cannot detect one. Likely causes include outdoor sensor not connected or wired incorrectly. There is no homeowner fix for this. You can reset once, but do not open the casing; book a Gas Safe registered engineer and quote the full code.
E.00.04 Baxi 600 Combi 2
Engineer after one resetSensors / thermistorsWhat it means
The return temperature sensor is disconnected.
Likely causes
Sensor fault or a loose sensor-to-board connection.
What you can safely do
Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if the code returns. Testing and replacing sensors means opening the casing, so this is engineer-only.
What does E.00.04 mean on a Baxi 600 Combi 2 boiler?
On a Baxi 600 Combi 2, E.00.04 means the return temperature sensor is disconnected. Likely causes include sensor fault or a loose sensor-to-board connection. There is no homeowner fix for this. You can reset once, but do not open the casing; book a Gas Safe registered engineer and quote the full code.
E.00.05 Baxi 600 Combi 2
Engineer after one resetSensors / thermistorsWhat it means
The return temperature sensor is short circuited.
Likely causes
Sensor fault or wiring.
What you can safely do
Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if the code returns. Testing and replacing sensors means opening the casing, so this is engineer-only.
What does E.00.05 mean on a Baxi 600 Combi 2 boiler?
On a Baxi 600 Combi 2, E.00.05 means the return temperature sensor is short circuited. Likely causes include sensor fault or wiring. There is no homeowner fix for this. You can reset once, but do not open the casing; book a Gas Safe registered engineer and quote the full code.
E.00.20 Baxi 600 Combi 2
Engineer after one resetSensors / thermistorsWhat it means
The flue gas temperature sensor is short circuited or reading below range.
Likely causes
Flue gas sensor or wiring.
What you can safely do
Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if the code returns. Testing and replacing sensors means opening the casing, so this is engineer-only.
What does E.00.20 mean on a Baxi 600 Combi 2 boiler?
On a Baxi 600 Combi 2, E.00.20 means the flue gas temperature sensor is short circuited or reading below range. Likely causes include flue gas sensor or wiring. There is no homeowner fix for this. You can reset once, but do not open the casing; book a Gas Safe registered engineer and quote the full code.
E.00.21 Baxi 600 Combi 2
Engineer after one resetSensors / thermistorsWhat it means
The flue gas temperature sensor is reading above range.
Likely causes
Flue gas sensor or wiring.
What you can safely do
Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if the code returns. Testing and replacing sensors means opening the casing, so this is engineer-only.
What does E.00.21 mean on a Baxi 600 Combi 2 boiler?
On a Baxi 600 Combi 2, E.00.21 means the flue gas temperature sensor is reading above range. Likely causes include flue gas sensor or wiring. There is no homeowner fix for this. You can reset once, but do not open the casing; book a Gas Safe registered engineer and quote the full code.
E.01.12 Baxi 600 Combi 2
Engineer after one resetSensors / thermistorsWhat it means
The return sensor is reading hotter than the flow sensor.
Likely causes
Sensors fitted the wrong way round or out of position, or a sensor fault.
What you can safely do
Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if the code returns. Testing and replacing sensors means opening the casing, so this is engineer-only.
What does E.01.12 mean on a Baxi 600 Combi 2 boiler?
On a Baxi 600 Combi 2, E.01.12 means the return sensor is reading hotter than the flow sensor. There is no homeowner fix for this. You can reset once, but do not open the casing; book a Gas Safe registered engineer and quote the full code.
E.04.01 Baxi 600 Combi 2
Engineer after one resetSensors / thermistorsWhat it means
The flow temperature sensor is short circuited.
Likely causes
Sensor or sensor-to-board connection.
What you can safely do
Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if the code returns. Testing and replacing sensors means opening the casing, so this is engineer-only.
What does E.04.01 mean on a Baxi 600 Combi 2 boiler?
On a Baxi 600 Combi 2, E.04.01 means the flow temperature sensor is short circuited. Likely causes include sensor or sensor-to-board connection. There is no homeowner fix for this. You can reset once, but do not open the casing; book a Gas Safe registered engineer and quote the full code.
E.04.02 Baxi 600 Combi 2
Engineer after one resetSensors / thermistorsWhat it means
The flow temperature sensor is disconnected.
Likely causes
Sensor or sensor-to-board connection.
What you can safely do
Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if the code returns. Testing and replacing sensors means opening the casing, so this is engineer-only.
What does E.04.02 mean on a Baxi 600 Combi 2 boiler?
On a Baxi 600 Combi 2, E.04.02 means the flow temperature sensor is disconnected. Likely causes include sensor or sensor-to-board connection. There is no homeowner fix for this. You can reset once, but do not open the casing; book a Gas Safe registered engineer and quote the full code.
PCB / electrical
H.03.05 Baxi 600 Combi 2
Safe checks firstPCB / electricalWhat it means
The power supply voltage is too low.
Likely causes
Low mains voltage at the property.
What you can safely do
Check whether lights are dimming or other appliances are struggling. If they are, contact an electrician or your electricity network operator (call 105 for a power cut). Then press reset once.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if your mains supply is fine and the code continues, so the boiler's own supply and board can be checked.
What does H.03.05 mean on a Baxi 600 Combi 2 boiler?
On a Baxi 600 Combi 2, H.03.05 means the power supply voltage is too low. Likely causes include low mains voltage at the property. Reset once; if the code comes back, book a Gas Safe registered engineer and quote the full code. Do not open the casing.
E.02.17 Baxi 600 Combi 2
Engineer after one resetPCB / electricalWhat it means
Permanent communication failure between the gas valve and the main board.
Likely causes
Electromagnetic interference or a main board fault.
What you can safely do
Write down the full code. Check the boiler has power and nothing else in the house has tripped, then switch the boiler off and on at its mains switch or press reset once. If the code comes back, leave the boiler off.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if the code returns. Board, wiring and gas valve checks mean opening the casing, so this is engineer-only.
What does E.02.17 mean on a Baxi 600 Combi 2 boiler?
On a Baxi 600 Combi 2, E.02.17 is listed in the manufacturer's table as "Permanent communication failure between the gas valve and the main board". There is no homeowner fix for this. You can reset once, but do not open the casing; book a Gas Safe registered engineer and quote the full code.
Other / controls
H.02.09 Baxi 600 Combi 2
Safe checks firstOther / controlsWhat it means
A blocking input or frost protection is active, so the boiler is partly stopped.
Likely causes
An external control holding the boiler off, a parameter setting or a wiring fault.
What you can safely do
Check any external timer, thermostat or frost control connected to the boiler is on. The code clears itself when the input is released.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if the code stays after you have checked the controls, or keeps coming back.
What does H.02.09 mean on a Baxi 600 Combi 2 boiler?
On a Baxi 600 Combi 2, H.02.09 means a blocking input or frost protection is active, so the boiler is partly stopped. Reset once; if the code comes back, book a Gas Safe registered engineer and quote the full code. Do not open the casing.
H.02.10 Baxi 600 Combi 2
Safe checks firstOther / controlsWhat it means
A blocking input signal has stopped the boiler completely.
Likely causes
An external control holding the boiler off, a parameter setting or a wiring fault.
What you can safely do
Check any external timer, thermostat or control connected to the boiler is on. The code clears itself when the input is released.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if the code stays after you have checked the controls, or keeps coming back.
What does H.02.10 mean on a Baxi 600 Combi 2 boiler?
On a Baxi 600 Combi 2, H.02.10 means a blocking input signal has stopped the boiler completely. Likely causes include an external control holding the boiler off, a parameter setting or a wiring fault. Reset once; if the code comes back, book a Gas Safe registered engineer and quote the full code. Do not open the casing.
Baxi 600 Combi (624 / 630, first generation)
These Baxi combis flash an E symbol followed by a two- or three-digit number, e.g. E133.
Source: Baxi Combi 624–630 Installation and Service Manual, doc. 7679306-1 (10/08/2017), p. 64, section 10.1 Error codes (Fig. 69). Open the manual (PDF) (Copy hosted by a UK trade site (no manufacturer-hosted copy found))
Ignition / flame
E09 Baxi 600 Combi (624/630)
Engineer after one resetIgnition / flameWhat it means
Gas valve connection cable fault.
Likely causes
Gas valve lead or connections; the manual says to check board connections and replace the board if it keeps happening.
What you can safely do
There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if the code comes back after one reset. Ignition and flame faults involve gas, so this is engineer-only.
What does E09 mean on a Baxi 600 Combi boiler?
On a Baxi 600 Combi, E09 is listed in the manufacturer's table as "Gas valve connection cable fault". There is no homeowner fix for this. You can reset once, but do not open the casing; book a Gas Safe registered engineer and quote the full code.
E15 Baxi 600 Combi (624/630)
Engineer after one resetIgnition / flameWhat it means
Gas valve fault.
Likely causes
Gas valve or its control from the board.
What you can safely do
There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if the code comes back after one reset. Ignition and flame faults involve gas, so this is engineer-only.
What does E15 mean on a Baxi 600 Combi boiler?
On a Baxi 600 Combi, E15 is listed in the manufacturer's table as "Gas valve fault". Likely causes include gas valve or its control from the board. There is no homeowner fix for this. You can reset once, but do not open the casing; book a Gas Safe registered engineer and quote the full code.
E128 Baxi 600 Combi (624/630)
Safe checks firstIgnition / flameWhat it means
Flame failure during normal operation.
Likely causes
Interrupted gas supply, low gas pressure, a frozen or blocked condensate pipe, or an electrode, flue or gas valve problem.
What you can safely do
Check another gas appliance such as the hob works, the gas meter valve is on and, on a prepayment meter, there is credit. In freezing weather, check the plastic condensate pipe outside: if it is frozen, pour warm (not boiling) water along it. Then press reset once. If the code comes back, stop resetting.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if the gas supply is fine and the code returns after one reset. Ignition and flame faults involve gas, so this is engineer-only.
What does E128 mean on a Baxi 600 Combi boiler?
On a Baxi 600 Combi, E128 is listed in the manufacturer's table as "Flame failure during normal operation". Check another gas appliance works, the meter valve is on and any prepay meter has credit, then reset once. If it returns, book a Gas Safe registered engineer.
E133 Baxi 600 Combi (624/630)
Safe checks firstIgnition / flameWhat it means
Interruption of the gas supply or flame failure: the boiler could not light or prove a flame.
Likely causes
Gas off, an empty prepayment meter, low gas pressure, a frozen condensate pipe, or a spark/sensing electrode, lead or gas valve fault.
What you can safely do
Check another gas appliance such as the hob works, the gas meter valve is on and, on a prepayment meter, there is credit. In freezing weather, check the plastic condensate pipe outside: if it is frozen, pour warm (not boiling) water along it. Then press reset once. If the code comes back, stop resetting.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if the gas supply is fine and the code returns after one reset. Ignition and flame faults involve gas, so this is engineer-only.
What does E133 mean on a Baxi 600 Combi boiler?
On a Baxi 600 Combi, E133 is listed in the manufacturer's table as "Interruption of the gas supply or flame failure: the boiler could not light or prove a flame". Check another gas appliance works, the meter valve is on and any prepay meter has credit, then reset once. If it returns, book a Gas Safe registered engineer.
E135 Baxi 600 Combi (624/630)
Safe checks firstIgnition / flameWhat it means
Interruption of the gas supply, listed in the manual as an internal error.
Likely causes
Gas supply interruption or a control board fault.
What you can safely do
Check another gas appliance such as the hob works, the gas meter valve is on and, on a prepayment meter, there is credit. In freezing weather, check the plastic condensate pipe outside: if it is frozen, pour warm (not boiling) water along it. Then press reset once. If the code comes back, stop resetting.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if the gas supply is fine and the code returns after one reset. Ignition and flame faults involve gas, so this is engineer-only.
What does E135 mean on a Baxi 600 Combi boiler?
On a Baxi 600 Combi, E135 is listed in the manufacturer's table as "Interruption of the gas supply, listed in the manual as an internal error". Check another gas appliance works, the meter valve is on and any prepay meter has credit, then reset once. If it returns, book a Gas Safe registered engineer.
E384 Baxi 600 Combi (624/630)
Engineer after one resetIgnition / flameWhat it means
False flame: a flame signal is detected when there should be none.
Likely causes
Electrode or wiring fault, moisture, a gas valve not closing, or the board.
What you can safely do
There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if the code comes back after one reset. Ignition and flame faults involve gas, so this is engineer-only.
What does E384 mean on a Baxi 600 Combi boiler?
On a Baxi 600 Combi, E384 is listed in the manufacturer's table as "False flame: a flame signal is detected when there should be none". There is no homeowner fix for this. You can reset once, but do not open the casing; book a Gas Safe registered engineer and quote the full code.
Water pressure / circulation
E109 Baxi 600 Combi (624/630)
Engineer after one resetWater pressure / circulationWhat it means
Pre-circulation fault: the boiler did not see water circulating before lighting.
Likely causes
Low pressure, air in the system, the pump or closed valves.
What you can safely do
There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if you have to top up more than once every few months, the gauge goes above about 2.5 bar when hot, water drips from the outside overflow pipe, or the code returns after topping up.
What does E109 mean on a Baxi 600 Combi boiler?
On a Baxi 600 Combi, E109 is listed in the manufacturer's table as "Pre-circulation fault: the boiler did not see water circulating before lighting". Reset once; if the code comes back, book a Gas Safe registered engineer and quote the full code. Do not open the casing.
E118 Baxi 600 Combi (624/630)
Safe checks firstWater pressure / circulationWhat it means
Primary system water pressure is too low (the manual says below 0.5 bar).
Likely causes
Water lost from the system through a leak, the pressure relief valve or bleeding radiators, or a flat expansion vessel.
What you can safely do
Look at the pressure gauge while the boiler is cold. If it is below about 1 bar, top it up with the filling loop exactly as your user guide shows, to about 1–1.5 bar or the figure in your guide, then close the loop fully. Check the radiator valves are open, then press reset once.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if you have to top up more than once every few months, the gauge goes above about 2.5 bar when hot, water drips from the outside overflow pipe, or the code returns after topping up.
What does E118 mean on a Baxi 600 Combi boiler?
On a Baxi 600 Combi, E118 means the primary system water pressure is too low (the manual says below 0.5 bar). With the boiler cold, check the pressure gauge; if it is below the level in your user guide, top it up as the guide shows, then reset once. If it returns, book a Gas Safe registered engineer.
E125 Baxi 600 Combi (624/630)
Engineer after one resetWater pressure / circulationWhat it means
Circulation fault in the primary circuit. The manual says it shows if the water temperature hardly changes 15 to 30 seconds after lighting, or overshoots the set temperature by 30 °C twice within 10 minutes.
Likely causes
Poor primary circulation: a stuck or failed pump, air, low pressure, closed valves or a blocked heat exchanger.
What you can safely do
There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if you have to top up more than once every few months, the gauge goes above about 2.5 bar when hot, water drips from the outside overflow pipe, or the code returns after topping up.
What does E125 mean on a Baxi 600 Combi boiler?
On a Baxi 600 Combi, E125 is listed in the manufacturer's table as "Circulation fault in the primary circuit". Reset once; if the code comes back, book a Gas Safe registered engineer and quote the full code. Do not open the casing.
E270 Baxi 600 Combi (624/630)
Engineer after one resetWater pressure / circulationWhat it means
Circulation fault (dry fire): the boiler detected it was firing without enough water flow.
Likely causes
Very low pressure, air, a stuck pump or closed valves.
What you can safely do
There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if you have to top up more than once every few months, the gauge goes above about 2.5 bar when hot, water drips from the outside overflow pipe, or the code returns after topping up.
What does E270 mean on a Baxi 600 Combi boiler?
On a Baxi 600 Combi, E270 is listed in the manufacturer's table as "Circulation fault (dry fire): the boiler detected it was firing without enough water flow". Reset once; if the code comes back, book a Gas Safe registered engineer and quote the full code. Do not open the casing.
Temperature / overheat
E110 Baxi 600 Combi (624/630)
Engineer after one resetTemperature / overheatWhat it means
The safety (overheat) thermostat has operated: the primary water overheated.
Likely causes
Poor circulation, low pressure, air, a stuck pump, or the thermostat or board.
What you can safely do
Let the boiler cool for 20 to 30 minutes, then press reset once. If the code comes back, leave the boiler off.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if the code comes back after one reset. Overheat shut-downs are safety devices doing their job, so this is engineer-only.
What does E110 mean on a Baxi 600 Combi boiler?
On a Baxi 600 Combi, E110 means the safety (overheat) thermostat has operated: the primary water overheated. There is no homeowner fix for this. You can reset once, but do not open the casing; book a Gas Safe registered engineer and quote the full code.
Flue / fan / air
E130 Baxi 600 Combi (624/630)
Engineer after one resetFlue / fan / airWhat it means
The flue NTC has operated (flue overheat).
Likely causes
Overheating flue gases, often linked to poor circulation or a blocked heat exchanger, or a sensor fault.
What you can safely do
There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if the terminal looks clear and the code returns. Flue and fan faults can affect how combustion gases leave your home, so this is engineer-only.
What does E130 mean on a Baxi 600 Combi boiler?
On a Baxi 600 Combi, E130 means the flue NTC has operated (flue overheat). There is no homeowner fix for this. You can reset once, but do not open the casing; book a Gas Safe registered engineer and quote the full code.
E160 Baxi 600 Combi (624/630)
Engineer after one resetFlue / fan / airWhat it means
Fan or fan wiring fault.
Likely causes
A failed fan, fan wiring or the control board.
What you can safely do
There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if the terminal looks clear and the code returns. Flue and fan faults can affect how combustion gases leave your home, so this is engineer-only.
What does E160 mean on a Baxi 600 Combi boiler?
On a Baxi 600 Combi, E160 is listed in the manufacturer's table as "Fan or fan wiring fault". Likely causes include a failed fan, fan wiring or the control board. There is no homeowner fix for this. You can reset once, but do not open the casing; book a Gas Safe registered engineer and quote the full code.
Sensors / thermistors
E20 Baxi 600 Combi (624/630)
Engineer after one resetSensors / thermistorsWhat it means
Central heating (flow) NTC sensor fault.
Likely causes
Failed sensor or wiring.
What you can safely do
Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if the code returns. Testing and replacing sensors means opening the casing, so this is engineer-only.
What does E20 mean on a Baxi 600 Combi boiler?
On a Baxi 600 Combi, E20 is listed in the manufacturer's table as "Central heating (flow) NTC sensor fault". Likely causes include failed sensor or wiring. There is no homeowner fix for this. You can reset once, but do not open the casing; book a Gas Safe registered engineer and quote the full code.
E28 Baxi 600 Combi (624/630)
Engineer after one resetSensors / thermistorsWhat it means
Flue NTC sensor fault.
Likely causes
Failed flue sensor or wiring.
What you can safely do
Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if the code returns. Testing and replacing sensors means opening the casing, so this is engineer-only.
What does E28 mean on a Baxi 600 Combi boiler?
On a Baxi 600 Combi, E28 is listed in the manufacturer's table as "Flue NTC sensor fault". Likely causes include failed flue sensor or wiring. There is no homeowner fix for this. You can reset once, but do not open the casing; book a Gas Safe registered engineer and quote the full code.
E40 Baxi 600 Combi (624/630)
Engineer after one resetSensors / thermistorsWhat it means
Central heating return NTC sensor fault.
Likely causes
Failed sensor or wiring.
What you can safely do
Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if the code returns. Testing and replacing sensors means opening the casing, so this is engineer-only.
What does E40 mean on a Baxi 600 Combi boiler?
On a Baxi 600 Combi, E40 is listed in the manufacturer's table as "Central heating return NTC sensor fault". Likely causes include failed sensor or wiring. There is no homeowner fix for this. You can reset once, but do not open the casing; book a Gas Safe registered engineer and quote the full code.
E154 Baxi 600 Combi (624/630)
Engineer after one resetSensors / thermistorsWhat it means
Flow/return sensor temperature test fault.
Likely causes
Flow and return sensors giving implausible readings, poor circulation or a sensor fault.
What you can safely do
Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if the code returns. Testing and replacing sensors means opening the casing, so this is engineer-only.
What does E154 mean on a Baxi 600 Combi boiler?
On a Baxi 600 Combi, E154 is listed in the manufacturer's table as "Flow/return sensor temperature test fault". There is no homeowner fix for this. You can reset once, but do not open the casing; book a Gas Safe registered engineer and quote the full code.
E321 Baxi 600 Combi (624/630)
Engineer after one resetSensors / thermistorsWhat it means
Hot water NTC sensor fault.
Likely causes
Failed hot water sensor or wiring.
What you can safely do
Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if the code returns. Testing and replacing sensors means opening the casing, so this is engineer-only.
What does E321 mean on a Baxi 600 Combi boiler?
On a Baxi 600 Combi, E321 is listed in the manufacturer's table as "Hot water NTC sensor fault". Likely causes include failed hot water sensor or wiring. There is no homeowner fix for this. You can reset once, but do not open the casing; book a Gas Safe registered engineer and quote the full code.
Other / controls
E83 Baxi 600 Combi (624/630)
Engineer after one resetOther / controlsWhat it means
Communication error.
Likely causes
Lost communication between the boiler's electronics and its controls.
What you can safely do
There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
When to call a Gas Safe engineer
Call a Gas Safe registered engineer if the code stays after you have checked the controls, or keeps coming back.
What does E83 mean on a Baxi 600 Combi boiler?
On a Baxi 600 Combi, E83 is listed in the manufacturer's table as "Communication error". Likely causes include lost communication between the boiler's electronics and its controls. Reset once; if the code comes back, book a Gas Safe registered engineer and quote the full code. Do not open the casing.
Common questions
About Baxi fault codes
3 questions
Which Baxi fault codes can I usually deal with myself?
On the Baxi ranges in our guide, only these codes have a safe homeowner check first: E.04.15 (a blocked flue); E.01.04, E.04.10, E128, E133, E135, H.03.02, H.03.54 (gas supply or flame loss); A.02.06, E118, H.02.07 (low pressure). Reset once. Every other code needs a Gas Safe registered engineer.
Where can I find the official fault code list for my Baxi 600 Combi?
Baxi publishes the fault table in the installation and servicing manual for the 600 Combi (7679306-1 (10/08/2017), p. 64). CombiCert's fault code guide explains 19 codes from it. Check your data badge matches this model first, because codes differ between ranges. Write down the exact code before resetting, so the engineer can diagnose it faster.
Where can I find the official fault code list for my Baxi 600 Combi 2?
Baxi publishes the fault table in the installation and servicing manual for the 600 Combi 2 (7796561-03 (04/23), pp. 73–77). CombiCert's fault code guide explains 33 codes from it. Check your data badge matches this model first, because codes differ between ranges. Write down the exact code before resetting, so the engineer can diagnose it faster.
Codes by type: Baxi 600 Combi (624 / 630, first generation)
6 questions
Which Baxi 600 Combi fault codes relate to the flue, fan or air supply?
On the Baxi 600 Combi, the manufacturer's table has 2 flue, fan or air supply codes: E130, E160. None of these has a homeowner fix beyond one reset. Do not open the casing; book a Gas Safe registered engineer and quote the full code.
Which Baxi 600 Combi fault codes mean the boiler will not light or loses its flame?
On the Baxi 600 Combi, the manufacturer's table has 6 ignition or flame codes: E09, E128, E133, E135, E15, E384. For E128, E133, E135, first check the gas meter, prepay credit and another gas appliance, then reset once. The others need a Gas Safe registered engineer.
Which Baxi 600 Combi fault code relates to controls or other faults?
On the Baxi 600 Combi, the manufacturer's table has one controls or other code, E83. E83 is listed in the manufacturer's table as "Communication error". This code has no homeowner fix beyond one reset. Do not open the casing; book a Gas Safe registered engineer and quote the full code.
Which Baxi 600 Combi fault codes point to a temperature sensor fault?
On the Baxi 600 Combi, the manufacturer's table has 5 temperature sensor codes: E154, E20, E28, E321, E40. None of these has a homeowner fix beyond one reset. Do not open the casing; book a Gas Safe registered engineer and quote the full code.
Which Baxi 600 Combi fault code means the boiler is overheating?
On the Baxi 600 Combi, the manufacturer's table has one overheat code, E110. E110 means the safety (overheat) thermostat has operated: the primary water overheated. This code has no homeowner fix beyond one reset. Do not open the casing; book a Gas Safe registered engineer and quote the full code.
Which Baxi 600 Combi fault codes relate to water pressure or circulation?
On the Baxi 600 Combi, the manufacturer's table has 4 water pressure or circulation codes: E109, E118, E125, E270. For E118, first check the pressure gauge when cold and top up if low, as your user guide shows, then reset once. The others need a Gas Safe registered engineer.
Codes by type: Baxi 600 Combi 2 (24 / 30 / 36)
7 questions
Which Baxi 600 Combi 2 fault codes relate to the flue, fan or air supply?
On the Baxi 600 Combi 2, the manufacturer's table has 3 flue, fan or air supply codes: E.01.20, E.04.13, E.04.15. For E.04.15, first check from outside that the flue terminal is not blocked, then reset once. The others need a Gas Safe registered engineer.
Which Baxi 600 Combi 2 fault codes mean the boiler will not light or loses its flame?
On the Baxi 600 Combi 2, the manufacturer's table has 7 ignition or flame codes: E.01.04, E.04.10, E.04.12, E.04.17, E.04.54, H.03.02, H.03.54. For E.01.04, E.04.10, H.03.02, H.03.54, first check the gas meter, prepay credit and another gas appliance, then reset once. The others need a Gas Safe registered engineer.
Which Baxi 600 Combi 2 fault codes relate to controls or other faults?
On the Baxi 600 Combi 2, the manufacturer's table has 2 controls or other codes: H.02.09, H.02.10. None of these has a homeowner fix beyond one reset. Do not open the casing; book a Gas Safe registered engineer and quote the full code.
Which Baxi 600 Combi 2 fault codes point to a control board or electrical fault?
On the Baxi 600 Combi 2, the manufacturer's table has 2 control board or electrical codes: E.02.17, H.03.05. None of these has a homeowner fix beyond one reset. Do not open the casing; book a Gas Safe registered engineer and quote the full code.
Which Baxi 600 Combi 2 fault codes point to a temperature sensor fault?
On the Baxi 600 Combi 2, the manufacturer's table has 8 temperature sensor codes: A.00.34, E.00.04, E.00.05, E.00.20, E.00.21, E.01.12, E.04.01, E.04.02. None of these has a homeowner fix beyond one reset. Do not open the casing; book a Gas Safe registered engineer and quote the full code.
Which Baxi 600 Combi 2 fault codes mean the boiler is overheating?
On the Baxi 600 Combi 2, the manufacturer's table has 5 overheat codes: E.04.03, E.04.08, H.01.08, H.01.14, H.01.21. None of these has a homeowner fix beyond one reset. Do not open the casing; book a Gas Safe registered engineer and quote the full code.
Which Baxi 600 Combi 2 fault codes relate to water pressure or circulation?
On the Baxi 600 Combi 2, the manufacturer's table has 6 water pressure or circulation codes: A.02.06, E.01.17, H.00.42, H.01.05, H.01.18, H.02.07. For A.02.06, H.02.07, first check the pressure gauge when cold and top up if low, as your user guide shows, then reset once. The others need a Gas Safe registered engineer.
Code still showing? Book a repair
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Explanations are written by CombiCert from the manufacturer manuals listed, which you should check for your exact model. This page is general information, not a diagnosis. If you smell gas, call 0800 111 999.