Worcester Bosch 30i Junior Fault codes & diagnostics

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

Combi Natural Gas 30 kW 2012-2015 Discontinued

Replaced by: Greenstar 30i

This boiler uses LED flash patterns

Count the flashes in one repeating group before the pause. That number is your fault code. Do not reset until you have noted it. How to read fault codes →

Severity at a glance

Each cell = one fault code. Hover to identify.
5 Emergency 112 High 9 Medium 25 Low

All 151 documented codes

Tap any card for details

Fast flash

Your boiler has experienced a serious internal communication error or hardware failure that has caused it to shut down for safety.

High Engineer only £150-£450

Parts commonly replaced

  • Fan
  • Printed Circuit Board (PCB)
  • Code Plug

Related codes

2 pulses

Your boiler is accidentally stuck in a technician's testing mode and needs to be switched back to its normal operating setting.

Low DIY-safe £0-80

What to check first

  1. Locate the small selector switch on the control panel
  2. Ensure the switch is turned away from the 'minimum' or 'service' icons
  3. Press the Reset button to clear the flashing light

Parts commonly replaced

  • None
5 pulses

Your boiler is currently stuck in a manual testing mode normally used by engineers during a service.

Medium DIY-safe £0-80

What to check first

  1. Locate the service mode switch (often a small dial or toggle) on the control panel.
  2. Check if the switch has been accidentally moved to the 'Max' or 'Min' setting.
  3. Turn the switch back to its normal operating position (usually the middle or 'Off' position).
9A 361

Your boiler's internal computer parts do not recognise each other because an incorrect or incompatible control module has been installed.

High Engineer only £280-450

Parts commonly replaced

  • Burner Control Unit (PCB)
  • KIM (Boiler Identification Module)

Related codes

9A 362

Your boiler’s internal computer chip is incompatible or has been incorrectly identified, causing the system to shut down for safety.

High Engineer only £180-350

Parts commonly replaced

  • Heatronic Control Module (HCM)
  • Main Printed Circuit Board (PCB)

Related codes

9U 233

Your boiler's main internal computer has lost communication with its identification chip, meaning the system cannot safely operate or provide heating and hot water.

High Engineer only £180-450

Parts commonly replaced

  • Code Plug
  • Printed Circuit Board (PCB)
200 O

Your boiler is currently working correctly and is simply letting you know that it is in central heating mode.

Low DIY-safe

What to check first

  1. No action is required as this is an status update rather than a fault.
  2. Check your thermostat if you did not expect the heating to be on.
  3. Ensure radiators are turned on if you require heat in specific rooms.

Related codes

201

Your boiler is simply indicating that it is currently busy heating your water and there is no actual fault to worry about.

Low DIY-safe

What to check first

  1. Turn off any running hot water taps
  2. Check if the code disappears once the hot water is no longer in use
  3. Monitor the boiler for any alternative flashing lights if the water stays cold

Related codes

201 O

Your boiler is currently working to provide hot water to your taps and this code is simply a status update rather than a fault.

Low DIY-safe

What to check first

  1. Check if a hot water tap is currently turned on somewhere in the house
  2. Close any open hot water taps
  3. Wait a few moments for the boiler to return to standby mode or heating mode

Related codes

Showing 11–20 of 151
202

Your boiler is currently taking a brief pause and is waiting for the heating or hot water signals to communicate properly before it starts up.

Low DIY-safe £0-90

What to check first

  1. Check that your room thermostat or programmer is turned up and calling for heat
  2. Ensure the batteries in your wireless thermostat have not run out
  3. Wait up to 10 minutes to see if the boiler clears the message and starts automatically

Parts commonly replaced

  • Thermostat batteries
  • External heating controls (Programmer/Timer)

Related codes

202 O

Your boiler has temporarily paused its burner to prevent it from switching on and off too frequently, which helps protect the system from unnecessary wear.

Low DIY-safe

What to check first

  1. Wait 15 to 20 minutes for the anti-cycle timer to finish
  2. Check that your room thermostat is turned up higher than the current room temperature
  3. Ensure at least two radiator valves are fully open to allow heat to dissipate

Related codes

203

Your boiler is currently in standby mode and waiting for a signal from your thermostat or programmer to start heating.

Low DIY-safe £0-50

What to check first

  1. Check that your room thermostat is turned up higher than the current room temperature.
  2. Ensure your heating programmer or central heating timer is set to 'On' or 'Auto'.
  3. Check that the batteries in your wireless thermostat have not run out.

Parts commonly replaced

  • Thermostat batteries
  • External room thermostat
  • Programmer/Timer unit

Related codes

203 0

Your boiler is working perfectly fine and is simply waiting for a signal from your thermostat to start heating.

Low DIY-safe

What to check first

  1. Check if your room thermostat is turned up higher than the current room temperature.
  2. Ensure your heating programmer or timer is set to an 'ON' period.
  3. Replace the batteries in your wireless wall thermostat if the screen is blank.

Related codes

204

Your boiler is currently taking a temporary break because the water inside it is already hotter than the temperature you have requested.

Low DIY-safe £0-120

What to check first

  1. Check if your room thermostat or programmer is set too low
  2. Ensure your radiator valves are open to allow heat to dissipate
  3. Wait up to 15 minutes for the system to cool down naturally and restart

Parts commonly replaced

  • None (Normal Operation)
  • NTC Thermistor
  • External Thermostat

Related codes

204 O

Your boiler has paused because it detects that the water inside is currently hotter than the temperature you have requested.

Low DIY-safe £0-120

What to check first

  1. Check if your thermostat or timer has recently been turned down
  2. Wait up to 15 minutes for the system to naturally cool down
  3. Ensure your radiator valves are open to allow heat to dissipate

Parts commonly replaced

  • None (operational status)
  • Temperature Sensor (NTC thermistor)

Related codes

208

Your boiler is currently running at full power for a manual testing sequence and will not respond to your normal thermostat settings until this mode is turned off.

Low DIY-safe

What to check first

  1. Locate the small button with a 'flame' or 'bin' symbol on the control panel.
  2. Press and hold the button for at least 5 seconds.
  3. The display should return to showing the temperature or a green light, indicating it is back in normal operation.

Related codes

208 0

Your boiler is currently stuck in a professional test mode used by engineers to check emissions, often caused by a button being held too long or a recessed switch becoming stuck.

Low DIY-safe £0-80

What to check first

  1. Locate the chimney sweep button (indicated by a small radiator/bin icon) on the control panel.
  2. Press and hold the button for at least 5 seconds until the display returns to normal temperature readings.
  3. If the code persists, try turning the boiler off at the main power switch for 30 seconds and then back on.

Parts commonly replaced

  • Control fascia panel
  • Internal selector switch

Related codes

212

Your boiler is overheating because the water inside is heating up faster than the system can move it away.

High DIY-safe £120-£350

What to check first

  1. Check if any radiator valves are turned off and open them fully
  2. Ensure the boiler pressure gauge is between 1 and 1.5 bar
  3. Press the reset button to see if the fault clears

Parts commonly replaced

  • Circulating Pump
  • Flow Temperature Sensor
  • Main Heat Exchanger (De-scaling)

Related codes

224 V

Your boiler has switched itself off because it has detected an unsafe rise in temperature, usually caused by low water pressure or a blockage in the system.

High DIY-safe £80-220

What to check first

  1. Check the pressure gauge on the front of the boiler
  2. If the needle is below 1, use the grey filling link handle underneath the boiler to top up the water
  3. Once the pressure reaches 1.5 bar, press and hold the reset button for five seconds

Parts commonly replaced

  • Overheat Thermostat
  • Circulation Pump
  • Temperature Sensor (NTC)

Related codes

Showing 21–30 of 151
226

Your boiler has recorded that a physical diagnostic tool was plugged into it to view the internal error history.

Low DIY-safe £0-80

What to check first

  1. Press and hold the reset button for five seconds
  2. Monitor the display to see if the code clears
  3. If the code persists, contact a Gas Safe engineer to check the control board

Parts commonly replaced

  • None (Software reset usually sufficient)
  • Control Board (if fault persists)

Related codes

227 V

Your boiler is trying to light but cannot establish a flame, meaning your heating and hot water will not work.

High DIY-safe £120-350

What to check first

  1. Check if other gas appliances in your home, such as a hob, are still working to confirm gas supply.
  2. If you have a prepay meter, check that you have enough credit.
  3. Press and hold the reset button for five seconds to see if the boiler restarts.

Parts commonly replaced

  • Ignition Electrode
  • Flame Sensing Probe
  • Gas Valve
  • Printed Circuit Board (PCB)

Related codes

228 V

Your boiler thinks there is a flame burning even though the gas should be off, causing it to shut down for safety.

Emergency Engineer only £180-450

Parts commonly replaced

  • Gas valve
  • Ionisation electrode
  • Ignition lead

Related codes

235

Your boiler's internal computer chips are not communicating correctly because they have mismatched software versions.

High Engineer only £250-450

Parts commonly replaced

  • Heat Control Module (HCM)
  • Main PCB (Printed Circuit Board)

Related codes

260

Your boiler has detected that the water isn't heating up or circulating properly after the burner has ignited.

High DIY-safe £100-£250

What to check first

  1. Check if your radiator valves are open
  2. Ensure your external controls or thermostat are calling for heat
  3. Check that the boiler pressure is between 1 and 1.5 bar on the gauge

Parts commonly replaced

  • Flow Temperature Sensor
  • Circulating Pump
  • Overheat Thermostat

Related codes

265

Your boiler is temporarily limiting its power output to prevent overheating because it is struggling to move heat away from the unit quickly enough.

Medium DIY-safe £80-250

What to check first

  1. Check that all radiator valves are fully open
  2. Ensure the system pressure is between 1 and 1.5 bar on the gauge
  3. Bleed all radiators to remove trapped air
  4. Press the reset button to see if the fault clears

Parts commonly replaced

  • Central heating pump
  • Main heat exchanger (flushing)
  • System filter

Related codes

268

Your boiler is currently running a self-diagnostic check, which usually happens briefly after a reset or power cut.

Low DIY-safe £0-80

What to check first

  1. Wait up to 10 minutes for the test cycle to complete automatically
  2. Ensure there is no active demand for heating or hot water during this time
  3. If the code persists for over 30 minutes, try a manual reset of the boiler

Parts commonly replaced

  • None (Software reset)
  • Main Control Board (if stuck in loop)

Related codes

270

Your boiler is noting that the temperature is rising too quickly during its normal operation, which often suggests the water isn't moving through the system fast enough.

High DIY-safe £0-180

What to check first

  1. Check that all radiator valves are fully open
  2. Ensure the boiler pressure is between 1.0 and 1.5 bar
  3. Bleed any air from the radiators
  4. Press the reset button once the system has cooled

Parts commonly replaced

  • Central heating pump
  • Main heat exchanger (flushing)
  • Temperature sensors (NTC thermistors)

Related codes

283

Your boiler is currently behaving as normal and is simply going through its standard sequence to light the burner.

Low DIY-safe

What to check first

  1. Check if heating or hot water is being requested
  2. Monitor the boiler for a few minutes to see if the flame ignites
  3. If the code persists without the boiler firing, try resetting the boiler

Related codes

284

Your boiler has stopped working because the flame has failed to light, likely due to a problem with the internal gas control system.

High Engineer only £180-350

Parts commonly replaced

  • Gas valve
  • Electrode assembly
  • Printed Circuit Board (PCB)

Related codes

Showing 31–40 of 151
305

Your boiler is confused and thinks you are still running a hot tap elsewhere in the house, preventing it from switching back to heating mode.

Medium DIY-safe £100-220

What to check first

  1. Check that all hot water taps in the house are fully turned off.
  2. Ensure any thermostatic mixer showers are turned off and not leaking.
  3. Reset the boiler by turning the control knob to the 'Reset' position for five seconds.

Parts commonly replaced

  • DHW Flow Turbine
  • Flow Sensor Cable
  • Main PCB
305 0

Your boiler is temporarily pausing the hot water production to prevent itself from overheating or cycling too frequently.

Low DIY-safe

What to check first

  1. Wait 10 to 15 minutes for the anti-cycle timer to expire naturally
  2. Ensure your hot water taps are fully turned off
  3. Check that the boiler pressure gauge is within the green zone (usually 1 to 1.5 bar)

Related codes

306 V

Your boiler is still detecting a flame even after it has been told to shut off the gas, which is a safety concern that requires a professional inspection.

Emergency Engineer only £250-£450

Parts commonly replaced

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

Related codes

328

Your boiler has detected an issue with the electrical power supply coming into your home, meaning the internal computer cannot function correctly.

High Engineer only £250-450

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Mains Power Supply Cable

Related codes

356

Your boiler has detected that the electrical supply coming into your home is too weak or unstable for it to operate safely.

High Engineer only £100-350

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • External Voltage Regulator

Related codes

360

Your boiler's internal computer brain cannot communicate properly with its main control unit, preventing the heating and hot water from starting up.

High Engineer only £180-£350

Parts commonly replaced

  • Heat Control Module (HCM)
  • Main PCB (Control Board)

Related codes

360 V

Your boiler's internal computer chip is giving the wrong signal to the main control board, which has caused the system to stop working for safety.

High Engineer only £120-250

Parts commonly replaced

  • Code plug
  • Printed Circuit Board (PCB)

Related codes

815 W/B

Your boiler has detected a problem with a temperature sensor that monitors how heat is moving through your system, which may prevent your heating from working correctly.

Medium Engineer only £120-£200

Parts commonly replaced

  • Low loss header temperature sensor
  • NTC thermistor
  • Connecting wiring harness

Related codes

1010 O

Your boiler has lost its internal connection to the smart controls or sensors, meaning different parts of the system are no longer talking to each other.

High Engineer only £100-250

Parts commonly replaced

  • EMS-Bus wiring harness
  • External controller cable
  • PCB fuse

Related codes

1017 W

Your boiler has detected that the water pressure is too low for it to run safely and simply needs more water added to the system.

High DIY-safe £0-160

What to check first

  1. Locate the internal or external filling loop (usually a silver flexible hose under the boiler).
  2. Slowly open the valve(s) until you hear water flowing and watch the pressure gauge.
  3. Close the valves tightly once the needle reaches between 1 and 1.5 bar.

Parts commonly replaced

  • Filling loop
  • Pressure sensor
  • Automatic air vent

Related codes

Showing 41–50 of 151
1021 B

Your boiler is unable to provide hot water because the internal sensor responsible for monitoring its temperature has stopped communicating with the system.

Medium Engineer only £100-£170

Parts commonly replaced

  • DHW Temperature Sensor (NPT Thermistor)
  • Wiring harness / connector

Related codes

1022 B

Your boiler is struggling to accurately measure the temperature of your hot water, which usually means the internal sensor is either loose or has failed.

High Engineer only £90-160

Parts commonly replaced

  • NTC Hot Water Sensor
  • Wiring Harness

Related codes

1037 W

Your boiler is having trouble reading the temperature outside, which means it might not adjust its heating levels correctly for the weather.

Low Engineer only £90-160

Parts commonly replaced

  • Outside temperature sensor
  • External sensor wiring

Related codes

1065 B

Your boiler's internal sensor can no longer tell if there is enough water pressure to run safely, so the system has shut itself down as a precaution.

High Engineer only £140-£220

Parts commonly replaced

  • Water pressure sensor
  • Wiring harness

Related codes

1068 W

Your boiler is struggling to know how cold it is outside, which can prevent it from heating your home efficiently or at all.

Medium Engineer only £90-180

Parts commonly replaced

  • Weather compensation outdoor sensor
  • Sensor wiring harness
1073 W

Your boiler has stopped working because an internal sensor that monitors water temperature has developed an electrical fault.

High Engineer only £100-£180

Parts commonly replaced

  • Flow temperature NTC sensor
  • Sensor wiring harness

Related codes

1074 W

Your boiler has lost communication with the internal thermometer that monitors water temperature, causing the system to shut down for safety.

High Engineer only £90-160

Parts commonly replaced

  • Flow Temperature Sensor (NTC thermistor)
  • Connecting wiring harness

Related codes

1075 W

Your boiler has detected an electrical fault with an internal thermometer, causing the system to shut down for safety.

High Engineer only £90-160

Parts commonly replaced

  • NTC Temperature Sensor
  • Wiring harness

Related codes

1076 W

Your boiler has lost communication with a vital heat sensor, meaning it won't fire up because it cannot safely monitor its internal temperature.

High Engineer only £120-250

Parts commonly replaced

  • Temperature Sensor (NTC Thermistor)
  • Sensor Wiring Harness
  • Printed Circuit Board (PCB)

Related codes

2920 V

Your boiler has stopped working because it cannot confirm that the flame is burning safely, so it has shut down as a precaution.

High DIY-safe £100-£280

What to check first

  1. Check if other gas appliances, like a hob, are working to ensure gas is reaching the property
  2. Locate the reset button on the front of the boiler and hold it for five seconds
  3. Check if your gas meter has credit if you are on a prepay meter

Parts commonly replaced

  • Ionisation Electrode
  • Gas Valve
  • Ignition Lead

Related codes

Showing 51–60 of 151
2924 V

Your boiler has stopped working because its internal control system is unable to communicate with the gas valve that fuels the burner.

High Engineer only £220-380

Parts commonly replaced

  • Gas Valve
  • Printed Circuit Board (PCB)

Related codes

2925 V

Your boiler has stopped working because the internal control board is not receiving the correct electrical signal from the gas valve.

High Engineer only £180-450

Parts commonly replaced

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

Related codes

2927 B

Your boiler has lost its flame while running and cannot stay lit, meaning it will likely shut down to prevent damage.

High Engineer only £120-450

Parts commonly replaced

  • Ionisation Electrode
  • Gas Valve
  • Flame Sensing Lead
  • Printed Circuit Board (PCB)

Related codes

2946 V

Your boiler's internal computer chip is faulty or has been identified incorrectly, meaning the system cannot communicate with itself to start up.

High Engineer only £120-£250

Parts commonly replaced

  • Coding Plug
  • Control Board (PCB)

Related codes

2948 B

Your boiler is struggling to keep a flame alight, which is preventing it from providing you with consistent heating or hot water.

High Engineer only £90-250

Parts commonly replaced

  • Ionisation electrode
  • Ignition lead
  • Gas valve

Related codes

2950 B

Your boiler is trying to light itself but cannot detect a flame, meaning your heating and hot water have likely stopped working.

High Engineer only £120-280

Parts commonly replaced

  • Ionisation Probe
  • Gas Valve
  • Electrode Set

Related codes

2963 B

Your boiler has detected that a temperature sensor is sending an unusual signal, likely due to a loose wire or a faulty connection internally.

High Engineer only £90-180

Parts commonly replaced

  • Flow temperature sensor
  • Wiring harness
  • Heat exchanger sensor

Related codes

2964 B

Your boiler has detected that water isn't moving through the main heating unit quickly enough, often caused by a blockage or a pump issue.

High Engineer only £150-£450

Parts commonly replaced

  • Circulation Pump
  • Main Heat Exchanger
  • Flow Temperature Sensor

Related codes

2965 B

Your boiler has become too hot and has shut itself down for safety to prevent damage to the internal components.

High DIY-safe £120-£350

What to check first

  1. Check that all radiator valves are fully open to allow water to circulate
  2. Ensure your boiler pressure is between 1 and 1.5 bar on the gauge
  3. Switch the boiler off and on again to see if the system clears the heat after cooling
  4. Bleed your radiators to remove any trapped air that might be blocking water flow

Parts commonly replaced

  • Central heating pump
  • Main heat exchanger (flushing/cleaning)
  • Thermistor (NTC sensor)

Related codes

2966 B

Your boiler is heating up too quickly and has shut itself down to prevent damage, which usually means the water isn't moving through the system properly.

High DIY-safe £120-450

What to check first

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

Parts commonly replaced

  • Circulation pump
  • Main heat exchanger
  • Primary flow thermistor

Related codes

Showing 61–70 of 151
2967 B

Your boiler has detected that the water is heating up too quickly or unevenly, causing it to shut down to prevent overheating.

High DIY-safe £120-£350

What to check first

  1. Check that all radiator valves are fully open
  2. Ensure the system pressure gauge is between 1 and 1.5 bar
  3. Bleed all radiators to remove trapped air
  4. Restart the boiler using the reset button

Parts commonly replaced

  • Central heating pump
  • Main heat exchanger (flushing/descale)
  • Thermistor (NTC sensor)

Related codes

2970 B

Your boiler has detected that the water pressure in your radiators or pipes is dropping much faster than it should, which usually indicates a significant leak or a fault with the pressure relief system.

High DIY-safe £90-180

What to check first

  1. Check all radiators and visible pipework for signs of water leaks
  2. Top up the system pressure to 1.5 bar using the internal or external filling loop
  3. Monitor the pressure gauge; if it drops quickly again, call an engineer

Parts commonly replaced

  • Expansion Vessel
  • Pressure Relief Valve (PRV)
  • Automatic Air Vent
2971 B

Your boiler has detected that the water pressure is too low for it to run safely, likely due to a minor leak or air being trapped in the radiators.

High DIY-safe £60-180

What to check first

  1. Locate the filling loop (usually a silver flexible hose) underneath or near the boiler.
  2. Open the one or two valves on the loop until you hear water flowing and the pressure gauge reaches between 1 and 1.5 bar.
  3. Close the valves tightly and check if the fault code clears.
  4. Bleed your radiators to remove any trapped air, then re-check the pressure gauge.

Parts commonly replaced

  • Pressure sensor
  • Pressure sensor wiring harness
  • Filling loop valves

Related codes

A1

Your boiler's pump is running without enough water, likely because the system has lost pressure or the pump itself has become stuck.

High DIY-safe £180-350

What to check first

  1. Check the pressure gauge on the front of the boiler; if it is below 1.0 bar, top it up using the filling loop
  2. Ensure all radiator valves are open and any air has been bled from the system
  3. Restart the boiler to see if the fault clears after the pressure is restored

Parts commonly replaced

  • Circulating Pump
  • Automatic Air Vent
  • Pressure Relief Valve

Related codes

A1 281

Your boiler's internal pump is either jammed or struggling to move water because there is air trapped inside the system.

High DIY-safe £180-350

What to check first

  1. Check that your radiator valves are fully open
  2. Bleed your radiators to remove any trapped air from the system
  3. Check the boiler pressure gauge and top it up to 1.5 bar if it is too low
  4. Reset the boiler to see if the pump clears itself

Parts commonly replaced

  • Circulating Pump
  • Automatic Air Vent

Related codes

A3 317

Your boiler has detected an electrical fault with a sensor that monitors the safety of the exhaust gases, causing the system to shut down for protection.

High Engineer only £120-190

Parts commonly replaced

  • Flue gas temperature sensor
  • Wiring harness

Related codes

A7

Your boiler is struggling to accurately measure the temperature of your hot water, which usually means the hot water is either inconsistent or not heating up at all.

Medium Engineer only £90-160

Parts commonly replaced

  • Domestic Hot Water (DHW) NTC Sensor
  • Wiring harness connectors

Related codes

A8

Your boiler has lost its connection with your external wireless temperature controls, meaning it cannot receive the correct signals to turn on or off.

High DIY-safe £90-250

What to check first

  1. Check if the batteries in your room thermostat or programmer need replacing
  2. Ensure the wireless receiver plugged into the boiler is firmly in place
  3. Turn the boiler power off and on again to attempt to re-establish the connection

Parts commonly replaced

  • RF Receiver
  • Wireless Room Thermostat
  • Internal Wiring Harness

Related codes

A8 362

Your boiler is struggling because it isn't receiving a steady supply of electricity from your home's mains power or a internal control module has failed.

High Engineer only £180-450

Parts commonly replaced

  • Heat Control Module (HCM)
  • Printed Circuit Board (PCB)

Related codes

B1

Your boiler has lost its identity because a small internal computer chip is missing or not properly connected, causing the system to stop working for safety.

High Engineer only £100-250

Parts commonly replaced

  • Code Plug
  • Printed Circuit Board (PCB)
Showing 71–80 of 151
B7 257

Your boiler's computer brain has encountered a serious internal error and can no longer control the heating system safely.

High Engineer only £280-450

Parts commonly replaced

  • Main Printed Circuit Board (PCB)

Related codes

C1 264

Your boiler has detected a problem with the fan or air supply and has shut down as a safety precaution while it was running.

High Engineer only £180-450

Parts commonly replaced

  • Fan assembly
  • Air pressure switch
  • Main PCB

Related codes

C4 237

Your boiler's internal computer has developed a fault and can no longer control the heating process safely.

High Engineer only £250-£450

Parts commonly replaced

  • Heat Control Module (HCM)
  • Main Printed Circuit Board (PCB)

Related codes

C4 273

Your boiler's fan was spinning when it was supposed to be stopped, often caused by strong winds or a sensing fault.

Low DIY-safe £0-180

What to check first

  1. Press and hold the 'Reset' button for five seconds
  2. Ensure there are no external obstructions blocking the flue terminal outside
  3. Monitor the boiler for a recurring lockout which may indicate a part failure

Parts commonly replaced

  • Air Pressure Switch
  • Fan
  • Printed Circuit Board (PCB)

Related codes

C6

Your boiler has stopped working because the internal fan, which safely pushes exhaust fumes outside, is not spinning at the correct speed.

High Engineer only £220-£380

Parts commonly replaced

  • Fan assembly
  • Fan wiring harness
  • Printed Circuit Board (PCB)
C6 215

Your boiler has shut down because the internal fan is spinning faster than the system's safety limits allow.

High Engineer only £250-£450

Parts commonly replaced

  • Fan Assembly
  • Main Printed Circuit Board (PCB)
C6 216

Your boiler has stopped working because the fan that helps remove exhaust gases isn't spinning fast enough to operate safely.

High Engineer only £250-450

Parts commonly replaced

  • Fan assembly
  • Printed Circuit Board (PCB)
  • Air pressure switch

Related codes

C7 214

Your boiler has stopped working because the internal fan, which safely exhausts gases, is not spinning or starting up.

High Engineer only £280-450

Parts commonly replaced

  • Fan assembly
  • Printed Circuit Board (PCB)
  • Wiring harness

Related codes

C7 216

Your boiler's fan is not spinning fast enough to clear out exhaust fumes safely, which has caused the system to shut down for your protection.

High Engineer only £200-£450

Parts commonly replaced

  • Fan assembly
  • Fan wiring harness
  • Printed Circuit Board (PCB)

Related codes

C7 217

Your boiler has shut down because the internal fan, which safely clears exhaust gases, has suddenly stopped working while the heating was running.

High Engineer only £220-£450

Parts commonly replaced

  • Fan Assembly
  • Main Control Board (PCB)
  • Wiring Harness

Related codes

Showing 81–90 of 151
CC 800

Your boiler has lost communication with the outside temperature sensor, which means it cannot automatically adjust its performance based on the weather.

Low DIY-safe £90-160

What to check first

  1. Locate the external weather sensor on your outside wall
  2. Check for any obvious damage to the sensor or its wiring
  3. Press the Reset button on the boiler control panel

Parts commonly replaced

  • Outdoor weather compensation sensor
  • Sensor wiring

Related codes

CE 207

Your boiler has stopped working because there is not enough water in the system to operate safely.

High DIY-safe £0-120

What to check first

  1. Locate the internal or external filling loop (usually a silver braided hose underneath the boiler)
  2. Slowly open the small black lever(s) to allow water into the system
  3. Watch the pressure gauge and close the levers once it reaches between 1 and 1.5 bar
  4. Reset the boiler using the reset button

Parts commonly replaced

  • Filling loop
  • Expansion vessel
  • Pressure relief valve

Related codes

CE 266

Your boiler has stopped working because the internal pump that moves water around your pipes has failed its startup test.

High Engineer only £220-£450

Parts commonly replaced

  • Central heating pump
  • Printed Circuit Board (PCB)

Related codes

D1 240

Your boiler has detected a problem with the internal sensor that monitors the temperature of the water returning to the unit, causing it to stop heating for safety.

High Engineer only £100-£190

Parts commonly replaced

  • Return Water Temperature Sensor (NTC Thermistor)
  • Wiring harness connection

Related codes

D1 241

Your boiler has stopped working because it has lost its connection to the internal sensor that monitors the temperature of the water returning to the unit.

High Engineer only £90-160

Parts commonly replaced

  • Return temperature sensor (NTC thermistor)
  • Connecting wiring harness
D3 232

Your boiler has shut down because an external safety device, such as a thermostat or a condensate pump, has detected a problem and stopped the connection.

High DIY-safe £80-180

What to check first

  1. Check if your room thermostat or programmer has power and is set to 'on'.
  2. If you have a condensate pump, check if it is full of water or blocked.
  3. Ensure any external switches or emergency stop buttons haven't been accidentally bumped.

Parts commonly replaced

  • External Room Thermostat
  • Condensate Pump
  • Wiring harness

Related codes

D4 213

Your boiler is overheating because water is not flowing through the system quickly enough to carry the heat away.

High DIY-safe £120-350

What to check first

  1. Check if your central heating valves (TRVs) are turned under the 'off' or '0' setting and open them.
  2. Ensure the boiler pressure is between 1 and 1.5 bar on the front gauge.
  3. Check if any external bypass valves are closed and open them.

Parts commonly replaced

  • Circulating Pump
  • Flow/Return Thermistor
  • Main Heat Exchanger (De-scale)

Related codes

D4 271

Your boiler has identified that it is heating up too quickly or water isn't moving through the system properly, causing it to shut down to prevent overheating.

High DIY-safe £150-£450

What to check first

  1. Check that all radiator valves are fully open
  2. Ensure the boiler pressure is between 1 and 1.5 bar on the pressure gauge
  3. Check if the condensate pipe is frozen (if it is cold outside)
  4. Reset the boiler using the reset button

Parts commonly replaced

  • Circulating Pump
  • Flow and Return Thermistors
  • Main Heat Exchanger

Related codes

D4 286

Your boiler has shut down because it has detected that the water flowing back into it is dangerously overheating.

High Engineer only £120-£350

Parts commonly replaced

  • Return temperature sensor
  • Central heating pump
  • Main PCB

Related codes

D4 341

Your boiler is overheating because the water inside it is getting too hot too quickly, usually because it isn't moving through the system properly.

High DIY-safe £150-£350

What to check first

  1. Check if your radiator valves (TRVs) are all turned up to maximum
  2. Check that the boiler pressure is between 1 and 1.5 bar on the gauge
  3. Ensure there are no air locks by bleeding your radiators

Parts commonly replaced

  • Circulating Pump
  • Primary Heat Exchanger
  • Flow Temperature Sensor

Related codes

Showing 91–100 of 151
E2

Your boiler's temperature sensor has stopped communicating correctly, meaning the system cannot safely monitor how hot the water is and has shut down as a precaution.

High Engineer only £90-160

Parts commonly replaced

  • CH Flow NTC Sensor
  • Sensor Wiring Harness

Related codes

E2 222

Your boiler has stopped working because its internal temperature sensor is reporting a technical electrical fault.

High Engineer only £120-£220

Parts commonly replaced

  • Flow NTC thermistor
  • Wiring harness
  • Main PCB

Related codes

E2 223

Your boiler has stopped working because it has lost the connection to the internal sensor that monitors the temperature of the water.

High Engineer only £90-160

Parts commonly replaced

  • Flow temperature NTC sensor
  • Wiring harness
  • Main PCB

Related codes

E2 233

Your boiler has lost its connection to the internal thermometer that measures the temperature of the water heading to your radiators, causing it to stop following your heating demands.

High Engineer only £90-160

Parts commonly replaced

  • Flow temperature sensor (NTC thermistor)
  • Wiring harness connector

Related codes

E2 350

Your boiler has detected an electrical fault with the internal sensor that monitors water temperature, causing the system to shut down for safety.

High Engineer only £90-160

Parts commonly replaced

  • Flow temperature NTC sensor
  • Wiring harness connector

Related codes

E2 351

Your boiler has lost its connection to the component that monitors water temperature, causing the system to stop working for safety.

High Engineer only £90-160

Parts commonly replaced

  • Flow Temperature Sensor (NTC thermistor)
  • Wiring harness connecting the sensor

Related codes

E5 218

Your boiler has sensed that the water inside IT is getting too hot too quickly, causing it to shut down for safety.

High DIY-safe £120-350

What to check first

  1. Check that all radiator valves are fully open to allow water to circulate.
  2. Ensure there is no air trapped in the system by bleeding your radiators.
  3. Check that your boiler pressure is between 1 and 1.5 bar on the front gauge.

Parts commonly replaced

  • Circulating Pump
  • Overheat Thermostat
  • Temperature Sensor (NTC thermistor)

Related codes

E9

Your boiler has switched itself off because it has detected that the internal water temperature has become dangerously high.

High DIY-safe £120-£350

What to check first

  1. Check if your radiator valves are open to allow heat to escape the system
  2. Check your boiler pressure gauge and top up to 1.5 bar if it is too low
  3. Press and hold the reset button for five seconds once the boiler has cooled down

Parts commonly replaced

  • Overheat Thermostat
  • Central Heating Pump
  • Main Heat Exchanger Flush
E9 210

Your boiler has shut down because it detected that the exhaust gases are getting too hot, which is a safety mechanism to prevent damage to the internal components.

High Engineer only £140-£320

Parts commonly replaced

  • Flue gas sensor
  • Heat exchanger (cleaning or replacement)
  • Main PCB

Related codes

E9 219

Your boiler has switched itself off because it has detected an dangerously high internal temperature or a faulty internal sensor.

High Engineer only £120-£250

Parts commonly replaced

  • Overheat thermostat
  • Temperature sensor (NTC)
  • Main heat exchanger

Related codes

Showing 101–110 of 151
E9 220

Your boiler has shut down because it has detected an dangerously high temperature or an electrical fault in its internal safety sensor.

High Engineer only £120-£250

Parts commonly replaced

  • Safety temperature sensor (Overheat thermostat)
  • E9 sensor wiring harness
  • Main heat exchanger

Related codes

E9 224

Your boiler has shut down because it has detected internal temperatures that are too high, meaning it has effectively overheated to protect itself.

High Engineer only £120-280

Parts commonly replaced

  • Flue thermostat
  • Overheat limit thermostat
  • Main heat exchanger (cleaning or replacement)
  • Pump

Related codes

E9 276

Your boiler has shut down because it has detected that the water inside is becoming dangerously hot.

High DIY-safe £120-350

What to check first

  1. Check that all radiator valves are fully open
  2. Check that your system pressure is between 1 and 1.5 bar on the dial
  3. Wait 30 minutes for the unit to cool and then press the Reset button

Parts commonly replaced

  • Circulating Pump
  • Overheat Thermostat
  • Main Heat Exchanger (Flushing)

Related codes

E9 277

Your boiler has shut down because it has detected its internal water temperature is getting dangerously hot.

High DIY-safe £120-350

What to check first

  1. Check that all radiator valves are fully open
  2. Ensure the system pressure is between 1 and 1.5 bar on the pressure gauge
  3. Reset the boiler by holding the reset button for five seconds

Parts commonly replaced

  • Circulating Pump
  • Overheat Thermostat
  • Main Heat Exchanger

Related codes

E9 285

Your boiler has sensed that the water inside is getting too hot and has shut itself down to prevent damage or overheating.

High DIY-safe £120-280

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 and 1.5 bar on the front gauge.
  3. Check for any visible leaks around the pipework or radiators.

Parts commonly replaced

  • Circulating Pump
  • Return Temperature Sensor (NTC)
  • Main Heat Exchanger (Descaling)

Related codes

E9 318

Your boiler has sensed that it is getting too hot and has shut itself down as a safety precaution to prevent damage.

High Engineer only £120-220

Parts commonly replaced

  • Flue gas temperature sensor
  • Wiring harness
  • Heat exchanger cleaning

Related codes

EA

Your boiler has stopped working because it cannot light the gas flame required to generate heat and hot water.

High DIY-safe £100-£250

What to check first

  1. Check if other gas appliances in your home, like a hob, are working to confirm your gas supply is active.
  2. Ensure your prepaid gas meter has sufficient credit.
  3. If the weather is freezing, check if your external condensate pipe is frozen and thaw it with warm water.
  4. Press and hold the reset button for five seconds to see if the boiler restarts.

Parts commonly replaced

  • Ignition Electrode
  • Spark Lead
  • Gas Valve
  • Printed Circuit Board (PCB)

Related codes

EA 227

Your boiler has stopped working because it cannot light the gas or the flame has gone out unexpectedly.

High DIY-safe £100-£350

What to check first

  1. Check if other gas appliances, like your hob, are working to ensure gas is reaching the property
  2. Check that your prepay gas meter has credit
  3. Press and hold the Reset button for five seconds

Parts commonly replaced

  • Ignition Electrode
  • Flame Sensing Probe
  • Gas Valve
  • Printed Circuit Board (PCB)

Related codes

EA 229

Your boiler has lost its flame while it was running, which means it has stopped providing heating and hot water for safety.

High DIY-safe £100-£250

What to check first

  1. Check if other gas appliances in your home, like a hob, are working to confirm gas supply.
  2. Ensure your prepaid gas meter (if applicable) has enough credit.
  3. Check if the white plastic condensate pipe leading outside has frozen during cold weather.
  4. Press and hold the 'Reset' button for five seconds to restart the boiler.

Parts commonly replaced

  • Flame sensing electrode
  • Ignition lead
  • Gas valve

Related codes

EA 234

Your boiler has stopped working because the internal control board has lost electrical communication with the gas valve.

High Engineer only £180-£450

Parts commonly replaced

  • Gas valve wiring harness
  • Gas valve
  • Printed Circuit Board (PCB)

Related codes

Showing 111–120 of 151
EA 261

Your boiler's internal computer has encountered a critical communication error and has stopped working for safety.

High DIY-safe £280-450

What to check first

  1. Locate the reset button on the front control panel
  2. Press and hold the reset button for five seconds
  3. Wait for the boiler to restart and check if the flame ignites

Parts commonly replaced

  • Heat Control Module (HCM)
  • Printed Circuit Board (PCB)

Related codes

EA 269

Your boiler is trying to light itself but the ignition process is taking longer than it should, often because it cannot detect a flame once it has sparked.

High DIY-safe £90-250

What to check first

  1. Check that your gas prepayment meter has credit (if applicable)
  2. Check that other gas appliances in your home, like a hob, are working correctly
  3. Perform a reset by holding the reset button for five seconds

Parts commonly replaced

  • Ignition Electrode
  • Flame Sensing Probe
  • Gas Valve

Related codes

EC 256

Your boiler's computer has detected an internal electronic failure and has stopped working to protect the system.

High Engineer only £280-450

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Burner Control Unit

Related codes

EF 349

Your boiler is working harder than it should because water isn't moving through the system quickly enough to take away the heat.

Medium DIY-safe £100-£350

What to check first

  1. Check that all radiator valves are fully open
  2. Ensure the central heating system pressure is between 1 and 1.5 bar
  3. Bleed all radiators to remove trapped air
  4. Check for any visible leaks around the pipework

Parts commonly replaced

  • Circulation pump
  • Flow and Return thermistors
  • Central heating filter (cleaning/replacement)

Related codes

EH 258

Your boiler’s internal computer has developed a serious communication fault or hardware failure, meaning it can no longer control the heating process safely.

High Engineer only £280-450

Parts commonly replaced

  • Main PCB (Printed Circuit Board)
  • Heat Control Module (HCM)

Related codes

F0

Your boiler has experienced an internal electrical communication error, meaning the control board cannot talk to the parts that start the burner.

High Engineer only £180-450

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Ignition Leads
  • Programmer Interface Module

Related codes

F0 237

Your boiler's internal computer has encountered a software glitch or a communication error that is preventing it from starting safely.

High DIY-safe £250-450

What to check first

  1. Locate the reset button on the front control panel
  2. Press and hold the reset button for five seconds
  3. Wait for the boiler to restart; if the code returns, a gas engineer is required

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Wire harness

Related codes

F0 238

Your boiler has detected an internal electrical communication fault between the main control board and the gas valve, preventing it from lighting safely.

High Engineer only £180-450

Parts commonly replaced

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

Related codes

F0 239

Your boiler's internal computer or control hub has developed a fault and is unable to manage the heating process.

High Engineer only £280-500

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Heat Control Module (HCM)

Related codes

F0 242

Your boiler's internal computer has developed a logic error or electrical fault, which means it cannot tell the boiler how to operate safely.

High Engineer only £240-£450

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Heat Control Module (HCM)

Related codes

Showing 121–130 of 151
F0 258

Your boiler's electronic brains have encountered a critical internal error and can no longer communicate with the heating system.

High Engineer only £280-550

Parts commonly replaced

  • Heat Control Module (HCM)
  • Printed Circuit Board (PCB)

Related codes

F0 262

Your boiler's internal computer has developed a communication fault or an electronic failure, meaning it cannot safely control the heating process.

High Engineer only £280-550

Parts commonly replaced

  • Heat Control Module (HCM)
  • Main Printed Circuit Board (PCB)

Related codes

F0 272

Your boiler's internal computer brain is having trouble communicating or has failed, meaning the system cannot run safely.

High Engineer only £250-450

Parts commonly replaced

  • Heat Control Module (HCM)
  • Printed Circuit Board (PCB)

Related codes

F0 278

Your boiler's internal computer is having trouble communicating with its temperature sensors, meaning it cannot safely monitor the water temperature to start up.

High Engineer only £100-£220

Parts commonly replaced

  • NTC Temperature Sensor
  • Wiring Harness
  • Main PCB

Related codes

F0 279

Your boiler’s internal computer has suffered a serious electronic failure and can no longer safely control the burner.

High Engineer only £280-450

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • KIM (Key Identification Module)

Related codes

F0 280

Your boiler's electronic command centre is having trouble communicating or has developed a fault, meaning it cannot process commands to heat your home.

High Engineer only £250-£450

Parts commonly replaced

  • Heat Control Module (HCM)
  • Main Printed Circuit Board (PCB)

Related codes

F0 287

Your boiler's internal computer has developed a communication fault and cannot safely tell the burner to fire up.

High Engineer only £250-450

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • KIM identity plug

Related codes

F0 290

Your boiler’s internal computer has encountered a critical communication error and cannot operate the system.

High Engineer only £180-£350

Parts commonly replaced

  • Heat Cell Management (HCM) software chip
  • Printed Circuit Board (PCB)

Related codes

F1 259

Your boiler's internal computer brain or its memory chip has developed a fault and is struggling to communicate with the rest of the unit.

High Engineer only £280-550

Parts commonly replaced

  • Heat Control Module (HCM)
  • Printed Circuit Board (PCB)

Related codes

F1 263

Your boiler's internal computer has encountered a critical communication error and can no longer control the heating process safely.

High Engineer only £280-550

Parts commonly replaced

  • Heat Control Module (HCM)
  • Printed Circuit Board (PCB)

Related codes

Showing 131–140 of 151
F7

Your boiler thinks a flame is present even when it should be off, causing it to shut down for safety.

High Engineer only £120-350

Parts commonly replaced

  • Ionisation electrode
  • Control box (PCB)
  • Wiring harness

Related codes

F7 228

Your boiler thinks a flame is present even though it hasn't actually started the ignition process, causing it to shut down for safety.

High Engineer only £120-£350

Parts commonly replaced

  • Ionisation electrode
  • Ignition lead
  • Printed Circuit Board (PCB)

Related codes

F7 328

Your boiler has experienced a temporary interruption in its electrical power supply, causing it to restart and stop working.

High DIY-safe £0-120

What to check first

  1. Check if there has been a local power cut or if a fuse has tripped in your home fuse box.
  2. Press and hold the Reset button on the front of the boiler for five seconds.
  3. Wait for the boiler to complete its restart sequence to see if the heating and hot water resume.

Parts commonly replaced

  • None (Software reset)
  • Printed Circuit Board (PCB)

Related codes

FA

Your boiler is still detecting a flame even though it should have turned off, which is a safety concern that requires a professional inspection.

Emergency Engineer only £180-350

Parts commonly replaced

  • Gas valve
  • Flame sensing electrode
  • Control board (PCB)

Related codes

FA 306

Your boiler is still detecting a flame even though it has been told to turn off, which is a safety precaution that stops the boiler from running.

High Engineer only £120-350

Parts commonly replaced

  • Flame sensing electrode
  • Gas valve
  • Printed Circuit Board (PCB)

Related codes

FA 364

Your boiler has detected a potential internal gas leak within its control valve, which is a critical safety issue that prevents it from starting up.

Emergency Engineer only £220-380

Parts commonly replaced

  • Gas Valve
  • Control Board (PCB)

Related codes

FB 365

Your boiler has detected a potential internal gas leak and has shut down as a safety precaution.

Emergency Engineer only £280-450

Parts commonly replaced

  • Gas valve
  • Printed Circuit Board (PCB)

Related codes

FD

Your boiler thinks the reset button was pressed by mistake or for too long and just needs a quick second tap to clear the error.

Low DIY-safe

What to check first

  1. Locate the reset button on the front control panel.
  2. Press and release the reset button once (do not hold it down).
  3. Wait approximately 15 seconds for the boiler to restart into its normal mode.

Related codes

FD 231

Your boiler has lost its connection to the electrical power supply or has experienced a sudden power cut.

High DIY-safe £0-120

What to check first

  1. Check if there has been a local power cut in your street
  2. Check your home's main fuse box/consumer unit to see if a circuit breaker has tripped
  3. Switch the boiler's power spur off and back on again to reset the connection

Parts commonly replaced

  • None (External power issue)
  • Fuses

Related codes

H07

Your boiler has detected that the water pressure is too low, which is preventing your heating and hot water from working properly.

Medium DIY-safe £0-120

What to check first

  1. Locate the internal or external filling loop (braided silver hose) under the boiler.
  2. Slowly open the blue tap or use the white plastic key to let water into the system.
  3. Close the taps once the pressure gauge on the front of the boiler reaches between 1 and 1.5 bar.

Parts commonly replaced

  • Filling loop
  • Pressure sensor
  • Expansion vessel

Related codes

Showing 141–150 of 151
HrE

Your boiler is experiencing a critical electronic failure that is causing it to repeatedly restart itself, meaning it cannot provide heating or hot water.

High Engineer only £280-450

Parts commonly replaced

  • Main Printed Circuit Board (PCB)
  • Internal Wire Harness

Related codes

Light off

Your boiler is currently sitting in standby mode because it hasn't been told to turn on by your thermostat or timer.

Low DIY-safe £0-80

What to check first

  1. Check that your room thermostat is turned up higher than the current room temperature
  2. Ensure your central heating timer or programmer is set to 'On' or 'Auto'
  3. Replace the batteries in your wireless thermostat if the display is blank

Parts commonly replaced

  • Thermostat batteries
  • Room thermostat
  • External programmer
Light on

Your boiler is operating normally and is currently heating your home or water exactly as requested.

Low DIY-safe

What to check first

  1. Check your thermostat settings if you feel the house is too warm
  2. Turn down your radiators if specific rooms are overheating
  3. No action is required as this indicates normal operation
NO CODE 212

Your boiler is overheating because the water inside it is getting too hot too quickly, causing it to shut down for safety.

High DIY-safe £120-350

What to check first

  1. Check that all radiator valves (TRVs) are turned to the highest setting
  2. Ensure the boiler pressure gauge is between 1 and 1.5 bar
  3. Check if any bypass valves or external pumps have been accidentally switched off

Parts commonly replaced

  • Central heating pump
  • Flow temperature sensor (NTC)
  • Main heat exchanger (de-scaling)

Related codes

No light

Your boiler has lost power completely and is no longer responding, meaning it cannot provide heating or hot water.

High DIY-safe £120-350

What to check first

  1. Check if other appliances in the house have power
  2. Check your main consumer unit (fuse box) to see if a circuit has tripped
  3. Ensure the boiler's fused spur switch (usually near the boiler) is turned on

Parts commonly replaced

  • Internal Fuse
  • Printed Circuit Board (PCB)
  • Transformer
rE

Your boiler is undergoing a restart process after a fault has been cleared or because the reset button was pressed.

Low DIY-safe £0-120

What to check first

  1. Wait up to 30 seconds for the reset process to complete
  2. Check if the boiler returns to normal operation
  3. If the code persists or repeats, contact a Gas Safe engineer to investigate the underlying cause

Parts commonly replaced

  • No parts usually required for the reset itself
  • Ignition electrodes
  • PCB

Related codes

T1

Your boiler is currently running a self-diagnostic test to check if the ignition system is working correctly.

Low DIY-safe £0-120

What to check first

  1. Wait for the test to complete automatically
  2. If the code persists for more than a few minutes, try resetting the boiler by holding the reset button for five seconds

Parts commonly replaced

  • None (Normal operation)
  • Ignition Electrode
  • Spark Cable

Related codes

T2

Your boiler's fan is failing to start or communicate with the control board, preventing the system from heating up.

High Engineer only £250-450

Parts commonly replaced

  • Fan assembly
  • Printed Circuit Board (PCB)
  • Wiring harness

Related codes

T3

Your boiler is struggling to circulate water because the central pump is not functioning correctly.

High Engineer only £220-£380

Parts commonly replaced

  • Circulation Pump
  • Internal Pump Cable
  • Main Control Board

Related codes

T4

Your boiler is having trouble switching between the heating and hot water functions because an internal valve is stuck or failing its startup check.

High Engineer only £180-280

Parts commonly replaced

  • Three-way diverter valve
  • Diverter valve motor/actuator

Related codes

Showing 151–151 of 151
T6

Your boiler has detected an internal electrical problem while checking the safety system that monitors the flame.

High Engineer only £180-350

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Wiring harness

Related codes