Viessmann Vitodens 200-W B2HF System Fault codes & diagnostics

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

System Natural Gas 2020-present
Download the Viessmann Vitodens 200-W B2HF System manual The official installation & service manual (PDF) — the exact document these fault codes were verified against. PDF

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108 High 11 Medium 13 Low

All 132 documented codes

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A.11

Your boiler has stopped working because the water pressure inside your heating system is too low.

High DIY-safe £80-150

What to check first

  1. Locate the external filling loop, which is a flexible silver hose connected to two valves under your boiler.
  2. Open the valves slowly to allow mains water into the system until the pressure gauge reads between 1.0 and 1.5 bar.
  3. Close both valves tightly and check the display to see if the error has cleared.

Parts commonly replaced

  • Filling loop
  • Pressure relief valve
  • Expansion vessel

Related codes

A.12

Your boiler's internal clock has lost its memory because a small backup battery has run out of power.

Low DIY-safe £5-10

What to check first

  1. Locate the control panel (HMU) on the front of the boiler
  2. Identify the small circular battery slot containing the CR2032 coin cell
  3. Carefully swap the old battery for a new CR2032 battery and reset the time and date

Parts commonly replaced

  • CR2032 Lithium Battery

Related codes

A.18

Your boiler has detected that waste water is backing up inside the main heating unit, which is preventing it from running safely.

High Engineer only £100-220

Parts commonly replaced

  • Condensate trap
  • Condensate discharge pipe
  • Electrode block

Related codes

A.20

Your boiler is simply notifying you that it was unable to set a reminder for its next scheduled service.

Low DIY-safe £0-80

What to check first

  1. Navigate to the main menu on the control panel
  2. Go to 'Settings' and then 'Service'
  3. Attempt to manually reset the service interval or acknowledge the notification

Related codes

A.21

Your central heating system currently has too much water inside it, causing the internal pressure to rise above the safe limit.

High DIY-safe £90-180

What to check first

  1. Locate a radiator in your home, preferably upstairs.
  2. Place a cloth and a container underneath the radiator bleed valve.
  3. Use a radiator key to open the valve slightly and release water until the pressure gauge on the boiler drops to between 1.0 and 1.5 bar.

Parts commonly replaced

  • Pressure relief valve
  • Expansion vessel
  • Pressure sensor

Related codes

F.5

Your boiler has stopped working because it cannot correctly measure the temperature of the water leaving the unit due to a sensor or wiring fault.

High Engineer only £120-£200

Parts commonly replaced

  • Flow temperature sensor (NTC)
  • Wiring harness
  • Control PCB

Related codes

F.7

Your boiler is currently unable to heat your domestic hot water, meaning you will not have any hot water available from your taps or shower.

High Engineer only £150-350

Parts commonly replaced

  • DHW temperature sensor
  • Diverter valve motor
  • Diverter valve cartridge

Related codes

F.8

Your boiler is currently unable to heat your domestic hot water, meaning you will not have hot water available from your taps or shower.

High Engineer only £150-350

Parts commonly replaced

  • DHW temperature sensor
  • Diverter valve
  • PCB

Related codes

F.9

Your boiler has lost connection with the sensor that monitors your hot water temperature, which usually means it cannot heat your water safely or at all.

High Engineer only £120-220

Parts commonly replaced

  • DHW Outlet Temperature Sensor (NTC)
  • Wiring harness / lead connector

Related codes

F.10

Your boiler has identified a technical fault with the sensor that monitors your hot water temperature, which typically means you will not have reliable hot water.

High Engineer only £120-£210

Parts commonly replaced

  • DHW outlet temperature sensor (NTC)
  • Wiring harness / lead

Related codes

Showing 11–20 of 132
F.11

Your boiler is not detecting heat coming from your solar thermal panels, so it cannot use that energy to help warm your home or water.

Low Engineer only £120-250

Parts commonly replaced

  • Solar collector temperature sensor
  • Cylinder temperature sensor
  • Solar circuit pump

Related codes

F.12

Your boiler has detected that the solar thermal panels connected to your heating system are not currently producing hot water as expected.

Low Engineer only £120-250

Parts commonly replaced

  • Solar collector sensor
  • Solar pump
  • Flow sensor

Related codes

F.13

Your boiler has lost its connection to the sensor that measures the temperature outside, meaning it may not know how hard it needs to work to heat your home.

Low DIY-safe £90-180

What to check first

  1. Check the outside sensor for any obvious signs of physical damage or loose casing
  2. Inspect the visible cable running from the sensor for any breaks or animal damage
  3. Try resetting the boiler to see if the fault clears (it may be a temporary software glitch)

Parts commonly replaced

  • Outdoor temperature sensor
  • Sensor wiring/cabling

Related codes

F.14

Your boiler is struggling to work out how hard to run because its external weather thermometer has developed an electrical fault.

Medium Engineer only £110-190

Parts commonly replaced

  • Outside temperature sensor
  • Sensor wiring cable

Related codes

F.15

Your boiler has lost the ability to communicate with or receive heat from your solar thermal panels, meaning it cannot use free energy from the sun to help heat your water.

Low Engineer only £150-300

Parts commonly replaced

  • Solar collector temperature sensor
  • Solar pump module
  • Communication cable

Related codes

F.16

Your boiler is reporting that it is not receiving heat from your solar thermal panels to warm your hot water tank as expected.

Low Engineer only £120-250

Parts commonly replaced

  • Solar circuit temperature sensor
  • Solar pump
  • Solar fluid

Related codes

F.29

Your boiler has lost communication with a sensor that monitors the water temperature in your heating system's distribution hub.

Medium Engineer only £120-190

Parts commonly replaced

  • Low loss header temperature sensor (NTC)
  • Sensor wiring harness

Related codes

F.30

Your boiler has detected a technical fault with a sensor that monitors water temperature elsewhere in your heating system, which is preventing the boiler from running correctly.

High Engineer only £120-£220

Parts commonly replaced

  • Low loss header temperature sensor (NTC)
  • Sensor wiring harness
  • External system control module

Related codes

F.49

Your boiler has detected a persistent issue with the burner and has automatically shut itself down to prevent unsafe operation.

High Engineer only £150-350

Parts commonly replaced

  • Ionisation electrode
  • Gas valve
  • Ignition transformer
  • Control board

Related codes

F.50

Your boiler has detected an internal issue and has safely shut itself down to prevent damage, meaning you currently have no heating or hot water.

High Engineer only £150-350

Parts commonly replaced

  • Gas valve
  • Ignition electrode
  • Control board (PCB)

Related codes

Showing 21–30 of 132
F.57

Your boiler is currently ignoring the temperature settings from your wall thermostat and is running based solely on the weather outside or its own internal default settings.

Low Engineer only £100-250

Parts commonly replaced

  • External temperature sensor
  • Communication module
  • Control unit PCB

Related codes

F.58

Your boiler is operating in a basic mode because it has lost the signal from your room thermostat, meaning it cannot adjust its temperature based on how warm your home is.

Low Engineer only £120-250

Parts commonly replaced

  • Bus communication module
  • Room thermostat unit
  • Wiring harness

Related codes

F.59

Your boiler has stopped working because it isn't receiving enough electrical power to operate the burner safely.

High Engineer only £180-450

Parts commonly replaced

  • PCB (Printed Circuit Board)
  • Internal Wiring Harness
  • Low Voltage Transformer

Related codes

F.62

Your boiler has detected an internal error during the ignition process and has safely shut down to prevent it from firing improperly.

High Engineer only £180-350

Parts commonly replaced

  • Gas valve
  • Burner control unit
  • Ignition electrode

Related codes

F.63

Your boiler has detected a critical internal error in its main electronic control unit, causing it to shut down to prevent unsafe operation.

High Engineer only £250-500

Parts commonly replaced

  • Control unit (PCB)
  • Wiring harness

Related codes

F.67

Your boiler has detected an internal issue with the burner flame signal, causing it to shut down for safety reasons to prevent improper combustion.

High Engineer only £150-350

Parts commonly replaced

  • Ionisation electrode
  • Gas valve
  • Boiler control unit (PCB)

Related codes

F.68

Your boiler has detected an issue with the flame stability or air-gas supply and has shut down for safety.

High Engineer only £150-350

Parts commonly replaced

  • Gas valve
  • Fan
  • Ionisation electrode
  • Air intake/flue seal

Related codes

F.69

Your boiler has detected an internal issue and shut itself down as a safety precaution, meaning you currently have no heating or hot water.

High Engineer only £150-350

Parts commonly replaced

  • Ionization electrode
  • Gas valve
  • Burner control unit

Related codes

F.70

Your boiler's electronic control unit is experiencing an internal error and has safely shut down the system to prevent further issues.

High Engineer only £250-500

Parts commonly replaced

  • Main control board (PCB)
  • Communication module

Related codes

F.71

Your boiler has detected an internal issue with its temperature monitoring system and has automatically shut down to prevent damage.

High Engineer only £150-300

Parts commonly replaced

  • Flow temperature sensor
  • Return temperature sensor
  • Main PCB

Related codes

Showing 31–40 of 132
F.72

Your boiler has detected an issue with the temperature sensors that monitor the heating process, causing it to shut down for safety.

High Engineer only £180-350

Parts commonly replaced

  • Flow temperature sensor
  • Return temperature sensor
  • Main PCB

Related codes

F.73

Your boiler has detected an internal issue with the water pressure sensor, which is preventing it from safely lighting the burner.

High Engineer only £150-250

Parts commonly replaced

  • Pressure sensor
  • Wiring harness

Related codes

F.74

Your boiler has detected that the water pressure in the system is too low to operate safely, causing it to shut down to prevent damage.

High DIY-safe £0-120

What to check first

  1. Locate the external filling loop (usually a silver flexible hose under or near the boiler).
  2. Open the one or two taps on the filling loop slowly until you see the pressure gauge rise.
  3. Close the taps tight once the pressure reaches 1.5 bar, then reset the boiler.

Parts commonly replaced

  • Filling loop valves
  • Expansion vessel
  • Pressure sensor

Related codes

F.77

Your boiler's internal computer brain is having trouble reading or saving its settings, causing the system to stop working for safety.

High Engineer only £250-550

Parts commonly replaced

  • Electronic Control Unit (PCB)
  • HMI (Control Unit) Programming Key

Related codes

F.89

Your boiler has detected an internal communication error between its main control components, causing it to shut down for safety.

High Engineer only £150-300

Parts commonly replaced

  • Control unit
  • Wiring harness
  • Communication module

Related codes

F.91

Your boiler has detected an issue with an external accessory or control module and is running in a limited backup mode to keep you warm until it can be properly checked.

Medium Engineer only £150-300

Parts commonly replaced

  • Extension module
  • Communication cable
  • PCB

Related codes

F.92

Your boiler's internal computer brain is struggling to talk to one of its electronic control parts, causing the system to stop working.

High Engineer only £200-550

Parts commonly replaced

  • ADIO Electronics Module
  • Wiring Harness
  • Main PCB

Related codes

F.94

Your boiler's internal computer parts have stopped communicating with each other, preventing the system from operating correctly.

High Engineer only £250-£580

Parts commonly replaced

  • SDIO Electronics Module
  • SM1A Extension Module
  • Internal Wiring Harness

Related codes

F.100

Your boiler has stopped working because of a communication failure between its internal electronic parts, meaning the main controls can no longer talk to each other.

High Engineer only £180-450

Parts commonly replaced

  • Electronic Control PCB
  • PlusBus Wiring Loom
  • External Sensor Module

Related codes

F.104

Your boiler has detected an error with an external electronic add-on, meaning it is unsure how to control certain heating or hot water features.

Medium Engineer only £150-300

Parts commonly replaced

  • EM-EA1 extension module
  • Communication cable
  • Main PCB

Related codes

Showing 41–50 of 132
F.142

Your boiler has detected an internal issue and has safely shut itself down to prevent damage, meaning you currently have no heating or hot water.

High Engineer only £150-350

Parts commonly replaced

  • Ionisation electrode
  • Ignition transformer
  • Main control board

Related codes

F.160

Your boiler has detected an issue preventing it from lighting the flame, which means your heating and hot water have stopped working.

High Engineer only £150-300

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Ionisation probe
  • Control unit

Related codes

F.161

Your boiler has detected an issue with the burning process and has shut itself down to keep your home safe.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Ionisation probe
  • Control board

Related codes

F.163

Your boiler has detected an issue with the burner process and has shut itself down as a safety precaution to prevent further faults.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Burner assembly

Related codes

F.182

Your boiler is currently unable to heat your domestic hot water, meaning you will likely have no hot water coming out of your taps.

High Engineer only £150-350

Parts commonly replaced

  • DHW diverter valve
  • DHW flow sensor
  • DHW pump

Related codes

F.183

Your boiler has stopped heating your hot water supply, meaning your taps and shower will only run cold.

High Engineer only £150-300

Parts commonly replaced

  • Diverter valve motor
  • DHW sensor
  • Flow switch

Related codes

F.184

Your boiler has detected an internal error preventing the burner from lighting, which means your heating and hot water will not work until the fault is cleared.

High Engineer only £150-300

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Control unit

Related codes

F.185

Your boiler has detected an internal error preventing the burner from lighting, which means your heating and hot water will not work until the fault is cleared.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Control unit (PCB)
  • Flame rectification sensor

Related codes

F.299

Your boiler has lost its internal time and date settings, which may disrupt your heating schedules.

Low DIY-safe £0-120

What to check first

  1. Locate the control panel on the front of the boiler
  2. Navigate to the 'Settings' menu using the touchscreen
  3. Select 'Time and Date' and manually update them to the current values
  4. Confirm the changes and check if the fault code clears

Parts commonly replaced

  • HMI Touchscreen Control Unit
  • Internal backup battery

Related codes

F.342

Your boiler has detected an internal communication error between its main control components, causing it to shut down for safety.

High Engineer only £150-350

Parts commonly replaced

  • Main PCB
  • Communication cable
  • Control unit

Related codes

Showing 51–60 of 132
F.345

Your boiler has automatically shut down because it has detected that the internal water temperature has become dangerously high.

High DIY-safe £120-350

What to check first

  1. Check that all radiator valves are fully open and not turned off.
  2. Ensure the external magnetic filter is clean and not blocked.
  3. Press the 'Reset' button on the boiler control panel once to see if the system restarts.

Parts commonly replaced

  • High limit thermostat
  • Circulation pump
  • Overheat sensor (NTC)

Related codes

F.346

Your boiler has detected an internal issue and has safely shut itself down to prevent operation while it is not functioning correctly.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Ionisation probe
  • Control board

Related codes

F.348

Your boiler has detected an issue with the internal combustion process and has safely shut itself down to prevent unsafe operation.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Ionisation probe
  • Control board

Related codes

F.349

Your boiler has detected a problem with the burner operation and has automatically shut itself down for safety reasons.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Ionisation electrode
  • Gas valve
  • Control board

Related codes

F.350

Your boiler has detected an internal issue and has safely shut itself down to prevent damage, meaning you currently have no heating or hot water.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Control board

Related codes

F.351

Your boiler has detected an internal issue and has safely shut itself down to prevent any potential safety hazards.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Control unit (PCB)

Related codes

F.352

Your boiler has detected an issue with the burner ignition or combustion process and has shut itself down as a safety precaution.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Ionisation electrode
  • Gas valve
  • Control unit

Related codes

F.353

Your boiler has detected a minor inconsistency in the internal combustion process and is temporarily pausing to restart safely.

Medium Engineer only £120-250

Parts commonly replaced

  • Ionisation electrode
  • Ignition lead
  • Gas valve

Related codes

F.354

Your boiler has detected an issue that prevents the burner from igniting, meaning your heating and hot water will not work until this is cleared.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Ionisation probe
  • Control board

Related codes

F.355

Your boiler has detected a flame before it has even started the ignition process, which is a safety conflict that prevents the system from running.

High Engineer only £140-£350

Parts commonly replaced

  • Ionisation electrode
  • Ignition lead
  • Burner control unit (PCB)

Related codes

Showing 61–70 of 132
F.357

Your boiler has detected an internal issue and has safely shut itself down to prevent further problems.

High Engineer only £150-300

Parts commonly replaced

  • Gas valve
  • Ignition electrode
  • Burner gasket
  • Control board

Related codes

F.359

Your boiler has detected an internal issue and has safely shut down the burner to prevent further problems.

High Engineer only £150-350

Parts commonly replaced

  • Ionisation electrode
  • Ignition transformer
  • Gas valve
  • Main PCB

Related codes

F.361

Your boiler is struggling to detect a flame when it tries to start, which means it cannot fire up to provide heating or hot water.

High DIY-safe £120-350

What to check first

  1. Check that your gas emergency control valve is in the 'on' position
  2. If you have a pre-payment meter, check that you have sufficient credit
  3. Press the 'Reset' button on the boiler control panel once

Parts commonly replaced

  • Ignition electrode
  • Ionisation probe
  • Gas valve

Related codes

F.365

Your boiler has detected that the burner is not firing correctly, which has caused it to stop working to prevent any potential safety issues.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Ionisation probe
  • Main control board

Related codes

F.366

Your boiler has stopped working because it failed to light or maintain a flame correctly, so it has shut itself down for safety reasons.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Ionisation probe
  • Control board

Related codes

F.367

Your boiler has detected an issue with the burning process and has automatically shut down to keep your home safe.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Ventilation/flue components

Related codes

F.369

Your boiler has detected an internal issue with the combustion system and has safely shut itself down to prevent damage or safety hazards.

High Engineer only £150-350

Parts commonly replaced

  • Gas valve
  • Burner assembly
  • Ignition electrode
  • Main circuit board

Related codes

F.370

Your boiler has detected a general issue preventing it from firing up, which means you currently have no central heating or hot water.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Control board

Related codes

F.372

Your boiler has detected an issue with the burner preventing it from firing, meaning your heating and hot water will not be working.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Ionisation probe
  • Control unit

Related codes

F.373

Your boiler has detected an internal issue and has safely shut down the burner to prevent damage, meaning you currently have no heating or hot water.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Ionisation electrode
  • Gas valve
  • Control board

Related codes

Showing 71–80 of 132
F.377

Your boiler has detected an internal issue and has safely shut itself down to prevent damage, meaning you currently have no heating or hot water.

High Engineer only £150-350

Parts commonly replaced

  • Gas valve
  • Control unit
  • Ignition electrode

Related codes

F.378

Your boiler has detected an internal issue with the combustion process and has stopped working to keep your home safe.

High Engineer only £180-350

Parts commonly replaced

  • Gas valve
  • Burner assembly
  • Control unit

Related codes

F.379

Your boiler has detected an issue with the internal combustion process and has safely shut itself down to prevent any further problems.

High Engineer only £150-300

Parts commonly replaced

  • Ionisation electrode
  • Ignition transformer
  • Gas valve

Related codes

F.380

Your boiler has detected a general issue with its internal combustion process and has safely shut itself down to prevent potential damage.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Ionisation probe
  • Gas valve
  • Control unit

Related codes

F.381

Your boiler has detected a general issue within the burner system and has automatically shut down to prevent further problems.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Ionisation probe
  • Control unit

Related codes

F.382

Your boiler has detected a problem with the burner's operation and has safely shut itself down to prevent potential issues.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Ionisation probe
  • Control board

Related codes

F.383

Your boiler has detected an internal issue that is preventing the burner from igniting, meaning you currently have no heating or hot water.

High Engineer only £150-350

Parts commonly replaced

  • Ionisation electrode
  • Ignition transformer
  • Gas valve
  • Main PCB

Related codes

F.384

Your boiler has detected an internal issue and has safely shut itself down to prevent any potential risks.

High Engineer only £150-350

Parts commonly replaced

  • Control unit
  • Ignition module
  • Wiring harness

Related codes

F.385

Your boiler has detected an internal issue and has shut itself down as a safety precaution to prevent damage.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Control board (PCB)

Related codes

F.386

Your boiler has detected an internal issue and has safely shut itself down to prevent potential damage, meaning you currently have no heating or hot water.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Control unit PCB
  • Ionization probe

Related codes

Showing 81–90 of 132
F.387

Your boiler has detected an internal issue that is preventing the burner from igniting, meaning your heating and hot water will not work until the fault is cleared.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Ionisation electrode
  • Gas valve

Related codes

F.388

Your boiler has detected a general issue with the burner and has safely shut itself down to prevent further problems.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Ionisation electrode

Related codes

F.395

Your boiler has detected an issue with the burner and has safely shut itself down to prevent potential damage or unsafe operation.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Ionisation probe
  • Control board

Related codes

F.396

Your boiler has detected an issue with the burner process and has shut itself down as a safety precaution to prevent unsafe operation.

High Engineer only £150-350

Parts commonly replaced

  • Ionisation electrode
  • Ignition transformer
  • Gas valve
  • Control unit

Related codes

F.399

Your boiler has detected an internal error preventing the burner from lighting, which means your heating and hot water will not work until the fault is cleared.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Control board

Related codes

F.400

Your boiler has detected a general issue with the burner's operation and has safely shut itself down to prevent further problems.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Ionisation probe
  • Control unit

Related codes

F.401

Your boiler has stopped heating because the burner has detected a safety fault and shut itself down to prevent any damage.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Ionisation electrode

Related codes

F.402

Your boiler has detected an issue with the burning process and has automatically shut down for safety reasons to prevent it from operating incorrectly.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Ionisation probe
  • Control board

Related codes

F.403

Your boiler has detected an internal issue with the burner and has safely shut itself down to prevent further problems.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Ionisation probe
  • Control unit

Related codes

F.404

Your boiler has detected an issue with the combustion process and has safely shut down to prevent unsafe operation.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Burner gasket

Related codes

Showing 91–100 of 132
F.405

Your boiler has detected an issue with the combustion process and has safely shut itself down to prevent it from running incorrectly.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Burner assembly
  • Ionisation probe

Related codes

F.406

Your boiler has detected an issue with the burner process and has shut down to keep your home safe.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Ionisation probe
  • Control board

Related codes

F.408

Your boiler has detected an internal issue that is preventing it from lighting safely, so it has shut down to protect your home.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Control board (PCB)

Related codes

F.410

Your boiler's main internal computer has encountered a critical processing error and can no longer control the burner safely.

High Engineer only £450-£700

Parts commonly replaced

  • BCU Burner Control Unit
  • HMI Operator Unit
  • Main PCB

Related codes

F.416

Your boiler has shut down because it detects that a safety sensor meant to monitor exhaust fumes is loose or installed incorrectly.

High Engineer only £90-180

Parts commonly replaced

  • Flue gas temperature sensor
  • Sensor retaining clip

Related codes

F.417

Your boiler has detected an internal issue and has automatically shut itself down for safety reasons to prevent further damage.

High Engineer only £150-300

Parts commonly replaced

  • Ionisation electrode
  • Gas valve
  • Control unit

Related codes

F.418

Your boiler has stopped working because its internal computer has lost power or has a broken electrical connection.

High Engineer only £180-450

Parts commonly replaced

  • Low voltage wiring harness
  • External Power Supply Unit
  • Main PCB

Related codes

F.425

Your boiler's internal computer is having difficulty processing its programmed settings, causing it to pause operations to prevent incorrect function.

High Engineer only £150-300

Parts commonly replaced

  • Main PCB
  • Control unit

Related codes

F.430

Your boiler is currently operating normally under automated control settings, and this code is simply a status message confirming it is working as expected.

Low DIY-safe

What to check first

  1. Check your boiler display for any actual error symbols.
  2. If no other issues are present, no action is required.
  3. Restart the boiler using the power button if you wish to clear the notification.

Related codes

F.446

Your boiler has detected an issue with the burner's ability to stay lit or ignite correctly and has shut down for your safety.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Ionisation probe
  • Burner gasket

Related codes

Showing 101–110 of 132
F.447

Your boiler has detected an internal error that has forced it to stop heating to ensure your home remains safe.

High Engineer only £150-350

Parts commonly replaced

  • Control unit
  • Gas valve
  • Ignition electrode

Related codes

F.448

Your boiler has detected an issue with the combustion process or burner ignition and has safely shut itself down to prevent further problems.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Ionisation probe
  • Gas valve
  • Control unit

Related codes

F.449

Your boiler has detected an issue with the burning process and has automatically shut itself down for safety reasons.

High Engineer only £150-300

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Burner gasket

Related codes

F.450

Your boiler has detected an issue with the burner's operation and has safely shut itself down to prevent potential damage.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Ionisation probe
  • Control unit

Related codes

F.451

Your boiler has detected an issue with the combustion process and has safely shut down to prevent it from running incorrectly.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Ionisation probe
  • Control unit

Related codes

F.452

Your boiler has detected an issue with the burner process and has shut itself down as a safety precaution to prevent further faults.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Burner control unit

Related codes

F.453

Your boiler has detected a persistent issue with the combustion process and has safely shut itself down to prevent unsafe operation.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Burner gasket
  • Control board

Related codes

F.454

Your boiler has detected an internal issue with the burner and has safely shut itself down to prevent operation while it is not functioning correctly.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Burner control unit

Related codes

F.455

Your boiler has detected an internal issue with the burner and has safely shut itself down to prevent further problems.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Ionisation probe
  • Control unit

Related codes

F.456

Your boiler has detected an issue with the combustion process and has safely shut itself down to prevent unsafe operation.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Flame rectification probe
  • Gas valve
  • Control board

Related codes

Showing 111–120 of 132
F.457

Your boiler has stopped working because it has detected an internal issue and triggered a safety shutdown to prevent further problems.

High Engineer only £150-350

Parts commonly replaced

  • Ionisation electrode
  • Ignition transformer
  • Printed circuit board

Related codes

F.458

Your boiler has stopped working because it has detected an internal issue and shut itself down for safety reasons.

High Engineer only £150-350

Parts commonly replaced

  • Ionisation electrode
  • Ignition transformer
  • Main PCB

Related codes

F.462

Your boiler has detected a general issue within its internal combustion system and has safely shut itself down to prevent further damage.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Main circuit board (PCB)
  • Ionization probe

Related codes

F.463

Your boiler has detected an issue with the burner's operation and has safely shut itself down to prevent potential problems.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Ionisation probe
  • Control board

Related codes

F.464

Your boiler has detected an issue with the burner process and has shut itself down as a safety precaution to prevent further faults.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Ionisation probe
  • Control board

Related codes

F.467

Your boiler has detected an issue with the burner ignition or combustion process and has safely shut itself down to prevent further problems.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Ionisation probe
  • Control board

Related codes

F.468

Your boiler has detected an issue with the burner and has safely shut itself down to prevent further problems.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Ionisation probe
  • PCB

Related codes

F.471

Your boiler is currently idle because it is not receiving a signal from your thermostat or hot water controller to provide heat.

Medium Engineer only £120-250

Parts commonly replaced

  • External controls
  • Wiring centre
  • Main PCB

Related codes

F.473

Your boiler is currently idle because it is not receiving a signal from your thermostat or heating controls to start producing heat.

Low DIY-safe

What to check first

  1. Check that your room thermostat or smart controller is set to a temperature higher than the current room temperature.
  2. Ensure your heating programmer or timer is set to 'On' or in a timed period.
  3. Check if your thermostat batteries need replacing or if your internet-connected controller has lost its Wi-Fi connection.

Parts commonly replaced

  • External heating controller
  • Thermostat
  • Bus communication module

Related codes

F.474

Your boiler has detected an internal issue and shut down for safety to prevent damage, meaning you currently have no heating or hot water.

High Engineer only £150-350

Parts commonly replaced

  • Ionisation electrode
  • Ignition transformer
  • Main control board

Related codes

Showing 121–130 of 132
F.517

Your boiler is struggling to communicate with its external control panel or thermostat, which may prevent it from receiving instructions to turn on your heating or hot water.

High Engineer only £120-250

Parts commonly replaced

  • Communication Module
  • Vitotrol Control Unit
  • System Wiring Harness

Related codes

F.527

Your boiler has detected an internal issue with the burner ignition process and has safely shut itself down to prevent any unsafe operation.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Burner control unit

Related codes

F.528

Your boiler has detected an issue with the combustion process and has safely shut itself down to prevent unsafe operation.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Control unit

Related codes

F.530

Your boiler has detected that the solar heating panels connected to your system are not operating at full efficiency.

Low Engineer only

Parts commonly replaced

  • Solar temperature sensor
  • Solar pump
  • Solar circuit pressure gauge

Related codes

F.540

Your boiler has detected an issue with the burner and has safely shut itself down to prevent unsafe operation.

High Engineer only £150-350

Parts commonly replaced

  • Ionisation electrode
  • Ignition transformer
  • Gas valve

Related codes

F.544

Your boiler has detected an issue with the valve that regulates the temperature of your heating water, so it has shut that valve to protect your system while keeping the water pump running.

Medium Engineer only £150-300

Parts commonly replaced

  • Mixing valve motor
  • Mixing valve assembly
  • Heating circuit control board

Related codes

F.545

Your boiler has detected an issue with the valve that regulates your heating temperature, causing it to shut down to prevent the system from getting too hot.

High Engineer only £180-350

Parts commonly replaced

  • Mixing valve motor
  • Mixing valve actuator
  • Heating circuit control board

Related codes

F.546

Your boiler has detected that the mixing valve is not positioning correctly, which may lead to your radiators failing to reach the desired temperature.

Medium Engineer only £150-300

Parts commonly replaced

  • Mixing valve actuator
  • Mixing valve assembly
  • PCB

Related codes

F.547

Your boiler has detected that the valve controlling the water temperature to your radiators has closed, which means your heating may not get as warm as you have set it.

Medium Engineer only £150-300

Parts commonly replaced

  • Mixing valve actuator
  • Mixing valve motor
  • Temperature sensor

Related codes

F.548

Your boiler has detected that the mixing valve is not operating correctly, which may lead to your radiators not reaching the desired temperature.

Medium Engineer only £150-300

Parts commonly replaced

  • Mixing valve motor
  • Mixing valve cartridge
  • Heating circuit control board

Related codes

Showing 131–132 of 132
F.549

Your boiler has detected an issue with the valve that regulates your heating temperature, causing it to shut off to prevent water from becoming too hot.

Medium Engineer only £150-300

Parts commonly replaced

  • Mixing valve actuator
  • Mixing valve assembly
  • Temperature sensor

Related codes

I.57

Your boiler has been temporarily stopped by an external device, such as a smart thermostat or a safety switch, which is telling the system not to run.

High DIY-safe £0-120

What to check first

  1. Check if your room thermostat or heating app is set higher than the current room temperature.
  2. Ensure any external switches or safety devices connected to the boiler are in the 'On' position.
  3. Restart the boiler using its power button to see if the external demand clears.

Parts commonly replaced

  • External Thermostat
  • Wiring Centre
  • Smart Control Hub

Related codes

8 operating states & engineer diagnostics

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

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