Baxi 224 Combi 2 Fault codes & diagnostics

29 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.

Combi Natural GasLPG 24 kW 2022-present
Choose your boiler type

The 224 range comes in 2 types

Pick the one you have. The fault codes, GC numbers and manual differ by type.

200 224 Combi 1 codes · 1 GC number 200 228 Combi 1 codes · 1 GC number
Each model has its own manual A family spans several manuals, one per model or generation. Pick your model above and its page has the manual its fault codes were read from.

The fault code is already on your display

Note it down before pressing reset — resetting clears the code immediately. How to read fault codes →

Severity at a glance

Each cell = one fault code. Hover to identify.
1 Emergency 28 High
Fault codes

All 29 documented codes

Tap any card for details

10

Your boiler has experienced a persistent error and has locked itself out for safety, requiring a manual restart to try and restore service.

High DIY-safe £80-250 Shared across the 224 Combi 2 range

What to check first

  1. Locate the reset button (on this model, it is often a button or a selector dial position marked 'R').
  2. Press or turn to the 'Reset' position and hold for 3-5 seconds.
  3. Wait for the boiler to attempt to restart; if the code returns immediately, do not attempt to reset again and call a professional.

Parts commonly replaced

  • Ignition Electrode
  • Printed Circuit Board (PCB)
  • Gas Valve
Full explanation for 10
E:00.04

Your boiler has stopped working because it cannot correctly read the temperature of the water returning from your radiators.

High Engineer only £90-160 Shared across the 224 Combi 2 range

Parts commonly replaced

  • Return temperature sensor (NTC thermistor)
  • Sensor wiring harness

Related codes

Full explanation for E:00.04
E:00.05

Your boiler has stopped working because it cannot correctly measure the temperature of the water returning from your radiators.

High Engineer only £90-160 Shared across the 224 Combi 2 range

Parts commonly replaced

  • Return NTC thermistor
  • Wiring harness
  • Main PCB

Related codes

Full explanation for E:00.05
E:01.04

Your boiler is struggling to keep its flame lit even after trying several times, which has caused it to stop working for safety reasons.

High Engineer only £100-250 Shared across the 224 Combi 2 range

Parts commonly replaced

  • Flame sensing electrode
  • Ignition lead
  • Gas valve
Full explanation for E:01.04
E:01.17

Your boiler has sensed that water is not moving around the system properly, which has caused it to shut down to prevent overheating.

High DIY-safe £150-450 Shared across the 224 Combi 2 range

What to check first

  1. Check the boiler pressure gauge and top it up to 1.5 bar if it is too low
  2. Ensure all radiator valves are turned on and not fully closed
  3. Check for any frozen pipes if the weather is extremely cold
  4. Reset the boiler by following the on-screen prompts or buttons

Parts commonly replaced

  • Circulation Pump
  • Main Heat Exchanger
  • Pump Lead

Related codes

Full explanation for E:01.17
E:01.20

Your boiler has shut down because the internal gases leaving the system have become dangerously hot, which usually suggests a serious internal blockage or a lack of water flow.

High Engineer only £150-£450 Shared across the 224 Combi 2 range

Parts commonly replaced

  • Main Heat Exchanger
  • Flue Thermostat
  • Water Pump
Full explanation for E:01.20
E:02.17

Your boiler's main control board has lost connection with the gas supply valve, meaning the system cannot safely light the flame to provide heating or hot water.

High Engineer only £180-450 Shared across the 224 Combi 2 range

Parts commonly replaced

  • Gas Valve Control Lead
  • Electronic Control Board (PCB)
  • Gas Valve
Full explanation for E:02.17
E:02.47

Your boiler has lost its digital connection to your thermostat or external controller, meaning it cannot receive instructions to turn the heating on.

High DIY-safe £0-120 Shared across the 224 Combi 2 range

What to check first

  1. Check if your smart thermostat or wall controller has run out of batteries.
  2. Ensure your internet router is turned on if you use a Wi-Fi-based heating app.
  3. Locate the wireless receiver (usually near the boiler) and check for power lights or try 're-pairing' the device as per your manual.

Parts commonly replaced

  • Batteries
  • External Thermostat Receiver
  • Communication Cable
Full explanation for E:02.47
E:04.00

Your boiler has detected a problem with how gas is flowing into the system and has shut down for safety.

Emergency Engineer only £280-450 Shared across the 224 Combi 2 range

Parts commonly replaced

  • Gas Valve
  • Printed Circuit Board (PCB)
  • Wiring Harness
Full explanation for E:04.00
E:04.01

Your boiler has stopped working because it cannot correctly measure the temperature of the water leaving the unit, leading to a safety shutdown.

High Engineer only £90-160 Shared across the 224 Combi 2 range

Parts commonly replaced

  • Flow Temperature Sensor (NTC Thermistor)
  • Wiring harness connectors

Related codes

Full explanation for E:04.01
Showing 11–20 of 29
E:04.02

Your boiler has stopped working because it can no longer accurately measure the temperature of the water leaving the unit.

High Engineer only £90-160 Shared across the 224 Combi 2 range

Parts commonly replaced

  • Flow Temperature Sensor (NTC Thermistor)
  • Sensor wiring harness

Related codes

Full explanation for E:04.02
E:04.03

Your boiler has shut down because it has detected a dangerously high internal temperature, which is usually caused by water failing to circulate properly through the system.

High DIY-safe £120-350 Shared across the 224 Combi 2 range

What to check first

  1. Check that all radiator valves are fully open to allow water to flow.
  2. Ensure your system water pressure is between 1.0 and 1.5 bar on the front display.
  3. Check for any visible blockages or frozen external condensate pipes.
  4. Reset the boiler by following the control panel instructions.

Parts commonly replaced

  • Circulation Pump
  • Heat Exchanger (de-scaling)
  • Flow Temperature Sensor (NTC thermistor)

Related codes

Full explanation for E:04.03
E:04.08

Your boiler has shut down because it has detected it is getting too hot, which is usually caused by a lack of water flow or a faulty sensor.

High DIY-safe £90-220 Shared across the 224 Combi 2 range

What to check first

  1. Check that your radiator valves are fully open to allow water to circulate.
  2. Ensure the boiler pressure is between 1.0 and 1.5 bar on the digital display.
  3. Try resetting the boiler by holding the 'R' or 'Reset' button for several seconds.

Parts commonly replaced

  • Overheat Thermostat
  • Temperature Sensor (NTC)
  • Circulating Pump
Full explanation for E:04.08
E:04.10

Your boiler has tried to light five times without success and has now locked itself out for safety.

High DIY-safe £100-280 Shared across the 224 Combi 2 range

What to check first

  1. Check that your gas emergency control valve is open and you have credit on your gas meter.
  2. Try to light another gas appliance, such as a hob, to ensure gas is reaching the property.
  3. Press the Reset button on the boiler control panel for several seconds.

Parts commonly replaced

  • Ignition electrode
  • Flame sensing probe
  • Gas valve
Full explanation for E:04.10
E:04.12

Your boiler thinks it sees a flame even though it hasn't started yet, causing it to shut down for safety.

High Engineer only £120-450 Shared across the 224 Combi 2 range

Parts commonly replaced

  • Ionization Electrode
  • Gas Valve
  • Printed Circuit Board (PCB)

Related codes

Full explanation for E:04.12
E:04.13

Your boiler's fan is unable to spin properly, which means the system has safely shut down to prevent waste gases from building up.

High Engineer only £250-£450 Shared across the 224 Combi 2 range

Parts commonly replaced

  • Extraction Fan
  • Fan Wiring Harness
  • Main PCB

Related codes

Full explanation for E:04.13
E:04.17

Your boiler has detected a failure with the unit that controls the flow of gas and air, meaning the heating and hot water will not work until it is safely repaired.

High Engineer only £250-£450 Shared across the 224 Combi 2 range

Parts commonly replaced

  • Gas valve
  • Gas/air unit manifold
  • Printed Circuit Board (PCB)

Related codes

Full explanation for E:04.17
H:01.00

Your boiler's internal computer has lost its connection with the gas control system, preventing the boiler from lighting safely.

High Engineer only £180-450 Shared across the 224 Combi 2 range

Parts commonly replaced

  • Wiring harness
  • Gas Valve
  • Printed Circuit Board (PCB)

Related codes

Full explanation for H:01.00
H:01.05

Your boiler is shutting down because the water inside is heating up much faster than it can circulate away, often due to a blockage or a pump issue.

High DIY-safe £120-£350 Shared across the 224 Combi 2 range

What to check first

  1. Check that all radiator valves are fully open
  2. Ensure the system pressure is between 1.0 and 1.5 bar
  3. Bleed all radiators to remove trapped air that may be blocking flow

Parts commonly replaced

  • Circulation Pump
  • Central Heating Filter (Clean/Service)
  • Flow and Return Temperature Sensors
Full explanation for H:01.05
H:01.08

Your boiler is overheating because the water inside it is heating up much faster than it can be pumped around your radiators.

High DIY-safe £120-£350 Shared across the 224 Combi 2 range

What to check first

  1. Check that all radiator valves (TRVs) are turned to the highest setting
  2. Ensure the boiler pressure is between 1.0 and 1.5 bar on the gauge
  3. Check for any visible blockages or closed bypass valves near the boiler
  4. Reset the boiler to see if the fault clears

Parts commonly replaced

  • Circulation Pump
  • Central Heating Filter
  • Main Heat Exchanger (Cleaning/Flush)

Related codes

Full explanation for H:01.08
Showing 21–29 of 29
H:01.14

Your boiler has shut down because it has detected that the water inside is getting too hot too quickly.

High DIY-safe £100-£350 Shared across the 224 Combi 2 range

What to check first

  1. Check that your radiator valves are open to allow water to flow.
  2. Ensure your system water pressure is between 1.0 and 1.5 bar on the gauge.
  3. Try resetting the boiler to see if the fault clears after the system cools down.

Parts commonly replaced

  • Central heating pump
  • Flow temperature sensor (NTC)
  • Main heat exchanger (flushing/cleaning)
Full explanation for H:01.14
H:01.18

Your boiler has stopped working because there is not enough water pressure in the system to circulate heat.

High DIY-safe £0-120 Shared across the 224 Combi 2 range

What to check first

  1. Locate the filling loop (usually two blue levers or a pull-down tap) underneath the boiler.
  2. Slowly open the valves until you hear water flowing and the pressure gauge reaches between 1.0 and 1.5 bar.
  3. Fully close the valves and restart the boiler.

Parts commonly replaced

  • Filling loop
  • Expansion vessel
  • Pressure sensor
Full explanation for H:01.18
H:01.21

Your boiler is shutting down because the water for your taps is heating up much quicker than it should, suggesting it isn't flowing through the system properly.

High Engineer only £120-£350 Shared across the 224 Combi 2 range

Parts commonly replaced

  • Plate Heat Exchanger
  • DHW Temperature Sensor (NTC)
  • Diverter Valve
Full explanation for H:01.21
H:02.02

Your boiler has lost its configuration settings and doesn't know how to operate properly, usually following a component replacement or power surge.

High Engineer only £80-120 Shared across the 224 Combi 2 range

Parts commonly replaced

  • Main PCB
  • Configuration plug

Related codes

Full explanation for H:02.02
H:02.03

Your boiler has been set up with the wrong internal software instructions and cannot run safely or efficiently.

High Engineer only £90-180 Shared across the 224 Combi 2 range

Parts commonly replaced

  • Main Printed Circuit Board (PCB)
  • Configuration plug

Related codes

Full explanation for H:02.03
H:02.04

Your boiler’s internal computer has encountered a configuration setting mistake, preventing it from starting up correctly.

High DIY-safe £100-£350 Shared across the 224 Combi 2 range

What to check first

  1. Locate the Reset button on the front control panel.
  2. Press and hold the Reset button for approximately 3 to 5 seconds.
  3. Wait for the boiler to restart and see if the code clears; if it recurs immediately, a professional is required.

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Parameter Key

Related codes

Full explanation for H:02.04
H:03.00

Your boiler has lost connection with a safety sensor that monitors exhaust gases, causing the system to shut down for protection.

High Engineer only £120-220 Shared across the 224 Combi 2 range

Parts commonly replaced

  • NTC Flue Sensor
  • Wiring harness
  • Main PCB

Related codes

Full explanation for H:03.00
H:03.01

Your boiler's main control panel cannot talk to the internal computer, meaning you cannot adjust settings or use the boiler as intended.

High Engineer only £180-350 Shared across the 224 Combi 2 range

Parts commonly replaced

  • HMI Control Board
  • Wiring Harness
  • Main PCB

Related codes

Full explanation for H:03.01
H:03.02

Your boiler has lost its flame while it was running, which means it cannot heat your water or your home.

High DIY-safe £100-£280 Shared across the 224 Combi 2 range

What to check first

  1. Check if other gas appliances (like a hob) are working to confirm gas supply
  2. Check that your gas prepayment meter has credit
  3. Ensure the condensate pipe (outside white plastic pipe) isn't frozen in cold weather
  4. Press the Reset button for five seconds

Parts commonly replaced

  • Flame sensing electrode
  • Gas valve
  • Ignition lead

Related codes

Full explanation for H:03.02
Status & diagnostic codes

7 operating states & engineer diagnostics

Not faults — these are normal operating states. Tap to expand.

AM001 Diagnostic Your boiler is simply notifying you that the hot water feature has been switched on, which is a normal setting rather than a fault. AM010 Diagnostic Your boiler's internal pump is having trouble regulating its speed or is not reporting it correctly, which may affect its ability to circulate heat. AM011 Diagnostic Your boiler is simply reminding you that its annual service is due soon to ensure it continues running safely and efficiently. AM012 Diagnostic Your boiler is currently reporting its internal operating status and is not indicating a specific hardware failure. AM014 Diagnostic Your boiler is undergoing a temporary internal safety check or update and should resume normal operation shortly. AM015 Diagnostic Your boiler's internal pump settings have been changed or disabled, meaning water cannot circulate to your radiators or taps. SVC Diagnostic Your boiler is simply displaying a reminder that it is due for its regular annual service to keep it running efficiently and safely.
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