Worcester Bosch Greenstar i Fault codes & diagnostics

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

Combi Natural GasLPG 24-30 kW 2005-present
GC Numbers 47-406-6047-406-6147-406-6247-406-6341-311-81
Download the Worcester Bosch Greenstar i manual The official installation & service manual (PDF) — the exact document these fault codes were verified against. PDF

The fault code is already on your display

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

Severity at a glance

Each cell = one fault code. Hover to identify.
3 Emergency 47 High 3 Medium 2 Low

Which version do you have?

The GC number on your boiler's data badge identifies the exact appliance and production years, as recorded in the UK Product Characteristics Database.

GC number Appliance (register name) Produced
47-406-60 Greenstar 25i ErP 2015–present
47-406-61 Greenstar 25i ErP LPG 2015–present
47-406-62 Greenstar 30i ErP 2015–present
47-406-63 Greenstar 30i ErP LPG 2015–present
41-311-81 430/I 2005–present

All 55 documented codes

Tap any card for details

9U 233

Your boiler's internal computer is not communicating correctly with the main control systems, meaning the boiler has safely shut down to prevent damage.

High Engineer only £250-450

Parts commonly replaced

  • HCM module
  • Main control board
235

Your boiler's internal computer is reporting that a piece of hardware is using software that doesn't match the rest of the unit, preventing it from functioning.

High Engineer only £150-300

Parts commonly replaced

  • HCM (Heatronic Control Module)
328

Your boiler's computer is having trouble reading the electricity supply coming from your home, which is causing it to lock itself to prevent damage.

High Engineer only £150-350

Parts commonly replaced

  • Main control board (PCB)
  • Wiring harness

Related codes

356

Your boiler is struggling because the electricity supply feeding it is weak, uneven, or cutting out momentarily.

Medium Engineer only £100-250

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Power cable/fused spur

Related codes

360

Your boiler's computer module does not match the internal controller, meaning the system cannot communicate properly to provide heating or hot water.

High Engineer only £150-250

Parts commonly replaced

  • HCM (Heating Control Module)
  • Control board unit
363

Your boiler is struggling to detect that the flame is lit, so it has safely shut itself down to prevent wasting gas.

High Engineer only £150-250

Parts commonly replaced

  • Ignition electrode
  • Ionisation probe
  • PCB

Related codes

A1 281

Your boiler's water pump is struggling to circulate water, which means the system cannot effectively move heat to your radiators or taps.

High Engineer only £150-300

Parts commonly replaced

  • Circulating pump
  • Pump head
  • Wiring harness
A7

Your boiler is struggling to accurately measure the temperature of your hot water, which usually means it cannot provide a consistent supply to your taps.

Medium Engineer only £90-160

Parts commonly replaced

  • Hot water NTC sensor
  • Sensor wiring harness

Related codes

A7 808

Your boiler is struggling to accurately detect the temperature of your hot water, which means it may fail to provide a consistent hot shower or turn the hot water off entirely.

Medium Engineer only £120-220

Parts commonly replaced

  • Domestic hot water NTC sensor
A8

Your boiler's internal components are having trouble communicating with the main control board, preventing the system from starting up.

High Engineer only £180-450

Parts commonly replaced

  • Main PCB (Printed Circuit Board)
  • Internal Wiring Harness
  • Display PCB

Related codes

Showing 11–20 of 55
A8 361

Your boiler's internal electronic 'brain' is not communicating correctly with the main control unit, preventing the system from operating.

High Engineer only £150-300

Parts commonly replaced

  • HCM module
  • Control board
AC

Your boiler has lost communication with its external heating controls or room thermostat, meaning it cannot receive signals to turn the heating on or off.

High DIY-safe £100-250

What to check first

  1. Check if the batteries in your room thermostat need replacing
  2. Ensure the thermostat is within range and not obstructed by large metal objects
  3. Reset the boiler to see if it re-establishes a connection with the controls

Parts commonly replaced

  • Room thermostat (TR2)
  • Wiring harness
  • RF Receiver
B1

Your boiler's internal computer brain cannot find its identity chip, which prevents it from operating safely.

High Engineer only £120-£250

Parts commonly replaced

  • Coding Plug
  • Printed Circuit Board (PCB)

Related codes

b7 257

Your boiler's main electronic brain has encountered a serious internal error and can no longer safely operate your heating or hot water.

High Engineer only £250-450

Parts commonly replaced

  • Control Board
  • HCM Module
C1 / 264

Your boiler has stopped working because the mechanical fan responsible for pushing out exhaust gases has unexpectedly stopped while the unit was running.

High Engineer only £200-350

Parts commonly replaced

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

Related codes

C4 / 273

Your boiler has detected that its exhaust fan has been running non-stop for the last day, so it has locked itself to prevent potential overheating or damage.

High Engineer only £150-250

Parts commonly replaced

  • Fan assembly
  • Printed Circuit Board (PCB)

Related codes

C4 237

Your boiler's computer system has encountered a critical communication error and can no longer safely operate the heating or hot water, requiring professional repair.

High Engineer only £250-450

Parts commonly replaced

  • Heatronic Control Module (HCM)
  • Main Control Board
C6

Your boiler's fan is spinning faster than it should, which is preventing the system from safely managing the air and gas flow needed for heating.

High Engineer only £180-£450

Parts commonly replaced

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

Your boiler has detected that the internal exhaust fan is spinning faster than it safely should, causing it to automatically shut down to prevent damage.

High Engineer only £200-350

Parts commonly replaced

  • Fan assembly
  • Printed Circuit Board (PCB)

Related codes

C6 / 216

Your boiler is struggling to push air through its system properly, which has forced it to shut down to stay safe.

High Engineer only £250-450

Parts commonly replaced

  • Fan assembly
  • Venturi
  • Wiring harness

Related codes

Showing 21–30 of 55
C7 / 214

Your boiler is unable to start up because the internal component responsible for moving air through the system is failing to engage.

High Engineer only £200-350

Parts commonly replaced

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

Related codes

C7 / 217

Your boiler has stopped working because the mechanical fan that pushes waste gases outside is not spinning as expected.

High Engineer only £180-350

Parts commonly replaced

  • Fan/Flue Fan
  • Printed Circuit Board (PCB)

Related codes

CC 800

Your boiler is struggling to read the outdoor temperature, so it has reverted to a standard internal setting to keep your home warm.

Low Engineer only £120-200

Parts commonly replaced

  • External temperature sensor
  • Wiring loom
Condensate pump failed

Your boiler has stopped working because the internal pump that removes waste water is not functioning, causing a safety shutdown to prevent a leak.

High Engineer only £140-£240

Parts commonly replaced

  • Condensate Pump Unit
  • Wiring Harness
  • Drainage pipework

Related codes

D4 341

Your boiler is getting too hot too quickly because the water inside isn't circulating properly, causing the system to shut down to prevent damage.

High Engineer only £150-350

Parts commonly replaced

  • Central heating pump
  • System filter
  • Diverter valve

Related codes

E2 / 222

Your boiler has stopped working because a sensor that measures the water temperature is sending a faulty reading, forcing the system to shut down for safety.

High Engineer only £150-250

Parts commonly replaced

  • NTC Sensor
  • Wiring harness
E2 / 223

Your boiler has lost its connection to the heat sensor, meaning it cannot tell how hot the water is and has safely shut down to prevent overheating.

High Engineer only £120-200

Parts commonly replaced

  • Flow temperature sensor
  • Wiring harness

Related codes

E2 / 350

Your boiler has stopped working because a sensor that measures the water temperature is reporting an impossible reading, preventing the unit from heating safely.

High Engineer only £120-200

Parts commonly replaced

  • NTC Sensor
  • Wiring harness

Related codes

E2 / 351

Your boiler has lost its connection to the component that measures the temperature of the water, so it has safely shut itself down to prevent overheating.

High Engineer only £120-220

Parts commonly replaced

  • NTC temperature sensor
  • Wiring harness

Related codes

E9

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

High DIY-safe £90-280

What to check first

  1. Check that your radiator valves are fully open to allow water to circulate.
  2. Ensure your boiler pressure is between 1 and 1.5 bar on the front gauge.
  3. Press the reset button to see if the fault clears after the system cools down.

Parts commonly replaced

  • Overheat Thermostat
  • Circulation Pump
  • Heat Exchanger (Flushing)

Related codes

Showing 31–40 of 55
E9 / 276

Your boiler has detected that the water inside has become dangerously hot and has shut itself down to prevent damage.

High Engineer only £150-300

Parts commonly replaced

  • Diverter valve
  • System pump
  • NTC temperature sensor
  • Heat exchanger

Related codes

E9 224

Your boiler has switched itself off because it has detected an unsafe temperature or a blockage in the exhaust flue, preventing it from operating safely.

Emergency Engineer only £150-300

Parts commonly replaced

  • High limit thermostat
  • NTC thermistor
  • Flue sensor
  • Primary heat exchanger

Related codes

EA

Your boiler has tried to light several times but cannot detect a flame, meaning it has locked itself out for safety.

High DIY-safe £100-£350

What to check first

  1. Check if other gas appliances, like a hob, are working to ensure gas is reaching the property
  2. Check if your gas meter credit has run out or if the semi-solid valve is bumped
  3. If it is freezing outside, check if your white plastic condensate pipe is frozen and defrost it with warm water
  4. Press and hold the 'Reset' button for five seconds

Parts commonly replaced

  • Ignition Electrode
  • Flame Sensor
  • Gas Valve
  • PCB

Related codes

EA / 227

Your boiler is trying to start but the flame is failing to establish or stay lit, so it has shut down for safety.

High Engineer only £150-300

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • PCB

Related codes

EA 227

Your boiler is trying to start but the flame is failing to light or stay lit, so it has shut down to keep you safe.

High Engineer only £120-250

Parts commonly replaced

  • Ignition electrode
  • Flame rectification probe
  • Gas valve

Related codes

EA 229

Your boiler has stopped because it can no longer detect the flame used to heat your water.

High Engineer only £150-300

Parts commonly replaced

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

Related codes

EA 261

Your boiler's main internal computer is failing to communicate properly, which has caused the system to shut down for safety.

High Engineer only £250-450

Parts commonly replaced

  • HCM (Heating Control Module)
  • Wiring harness

Related codes

EH 258

Your boiler has detected an internal software or electronic communication error that prevents it from operating safely.

High Engineer only £250-450

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Wiring harness

Related codes

F0 238

Your boiler is unable to safely control the gas flame, so it has shut itself down to prevent any risk of a gas leak.

High Engineer only £250-450

Parts commonly replaced

  • Gas valve
  • Control board
  • Wiring harness

Related codes

F0 239

Your boiler's main computer brain has detected an internal failure and can no longer safely operate, meaning your heating and hot water will not work.

High Engineer only £250-450

Parts commonly replaced

  • HCM (Heating Control Module)
  • Main Control Board

Related codes

Showing 41–50 of 55
F0 258

Your boiler has detected an internal electronic failure within its main brain, preventing it from operating safely.

High Engineer only £250-450

Parts commonly replaced

  • HCM (Heating Control Module)
  • Main Control Board
F0 262

Your boiler's internal computer is malfunctioning, meaning the system has safely shut down because it cannot correctly manage its heating and hot water functions.

High Engineer only £250-450

Parts commonly replaced

  • Main Control Board
  • HCM Module
F0 272

Your boiler's main electronic brain is failing to communicate correctly, which has caused the system to shut down for safety.

High Engineer only £250-450

Parts commonly replaced

  • Heating Control Module (HCM)
  • Main Control Board
F0 280

Your boiler's internal computer has encountered a critical error preventing it from operating safely.

High Engineer only £250-450

Parts commonly replaced

  • Printed Circuit Board (PCB)
F0 290

Your boiler's internal computer is experiencing a data processing error that prevents it from operating correctly.

High Engineer only £250-450

Parts commonly replaced

  • Printed Circuit Board (PCB)
F1 259

Your boiler's electronic brain has encountered a serious internal error and can no longer communicate with the rest of the unit, meaning it has shut down for safety.

High Engineer only £250-450

Parts commonly replaced

  • Heatronic Control Module (HCM)
  • Main Control Unit

Related codes

F1 263

Your boiler has detected a critical failure in its internal electronic brain, meaning it has safely shut itself down and cannot operate until the hardware is repaired.

High Engineer only £250-450

Parts commonly replaced

  • Control Board
  • HCM Module
F7

Your boiler thinks a flame is still burning even after it has been told to turn off, which is a safety conflict that stops the system from running.

High Engineer only £120-£350

Parts commonly replaced

  • Ionisation electrode
  • Printed Circuit Board (PCB)
  • Wiring harness

Related codes

F7 228

Your boiler has detected an unexpected signal that suggests it might not be safely detecting when the flame is actually on or off, so it has locked itself out to prevent a potential hazard.

High Engineer only £150-300

Parts commonly replaced

  • Flame rectification probe
  • Printed Circuit Board (PCB)
  • Ignition lead

Related codes

FA / 306

Your boiler has detected that a flame is present even though it has commanded the gas supply to shut off, which indicates a safety-related internal fault.

Emergency Engineer only £150-300

Parts commonly replaced

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

Related codes

Showing 51–55 of 55
FA 306

Your boiler has detected that a flame is present even after it has attempted to shut off the gas supply, which is a safety concern that prevents it from restarting.

Emergency Engineer only £150-300

Parts commonly replaced

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

Related codes

Fd

Your boiler has stopped because the reset button was held down for too long or pressed by mistake, causing a minor software confusion.

Low DIY-safe

What to check first

  1. Press the reset button briefly (less than one second).
  2. Wait for the display to clear and the boiler to restart.
  3. Ensure no other fault codes are appearing once the 'Fd' clears.

Related codes

Fd / 231

Your boiler has lost power while it was already trying to fix a separate error, so it is stuck in a confused state.

High Engineer only £120-250

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Control module

Related codes

H09

Your boiler has lost its connection to the water pump that circulates heat around your home, meaning it cannot safely provide heating or hot water.

High Engineer only £150-350

Parts commonly replaced

  • Central heating pump
  • Wiring harness
  • Printed Circuit Board (PCB)

Related codes

internal error

Your boiler's internal computer brain is having trouble communicating with its power supply, preventing the system from starting up.

High Engineer only £250-550

Parts commonly replaced

  • Main PCB (Control Board)
  • Transformer
  • Wiring Harness

25 operating states & engineer diagnostics

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

0.0 Diagnostic The number 0.0 indicates that you are currently viewing your boiler's internal memory log of the most recent error, rather than an active fault stopping the machine from working. 200 Status Your boiler is operating normally and is currently heating the water for your radiators. 201 Status Your boiler is currently operating normally by heating your hot water supply. 202 Status Your boiler is temporarily pausing between heating cycles to protect itself from unnecessary wear and tear. 203 Status Your boiler is currently in a waiting state where it has temporarily paused operation because it has reached the temperature set on your thermostat or controls. 204 Status Your boiler has temporarily paused heating because the water inside is already hotter than the temperature you have currently set. 208 Status Your boiler is currently set to a special testing mode used by engineers to check its performance, rather than a standard operating fault. 226 Diagnostic Your boiler is noting that a professional diagnostic tool has been plugged into it; this is an informational record rather than a sign of a mechanical failure. 265 Status Your boiler is perfectly healthy and is simply pausing because it is already warm enough and doesn't need to burn any more gas. 268 Status Your boiler is currently in a manual testing mode that was triggered via the settings menu, meaning it is performing diagnostic checks rather than heating your home as usual. 270 Status Your boiler is currently performing a routine start-up sequence and is just preparing itself to operate. 283 Status Your boiler is simply preparing to ignite and is currently going through its standard startup safety checks. 284 Status Your boiler is failing to ignite the flame needed to produce heat or hot water because it isn't detecting a successful start-up. 305 Status Your boiler is temporarily pausing to prevent excessive wear on its internal parts after you finished using your hot water tap. 357 Status Your boiler is simply running a routine 100-second self-cleaning cycle to remove trapped air from the system. 358 Status Your boiler is performing an automatic 'exercise' routine to keep its internal parts moving smoothly and prevent them from getting stuck, which is a normal maintenance feature. H-- Status Your boiler is operating normally and there are no currently recorded maintenance tasks or errors that require your attention. H03 Diagnostic Your boiler is simply reminding you that it is time for its annual safety service to ensure it continues running efficiently and safely. H08 Diagnostic Your boiler has reached its programmed service interval and is kindly reminding you that it is time for a routine professional safety check. H11 Diagnostic Your boiler is struggling to accurately measure the temperature of your hot water, which means it may be unable to heat it correctly for your taps. H13 Diagnostic Your boiler is simply reminding you that it is time for its annual safety service, as set by the installer, rather than indicating a mechanical breakdown. h13/H13 Diagnostic Your boiler is simply reminding you that its annual service is now due to keep it running safely and efficiently. H29 Diagnostic Your boiler has lost communication with the weather sensor outside your home, meaning it cannot automatically adjust its temperature based on outdoor conditions. II - Status Your boiler is performing a routine initial safety check to fill its internal drainage system after the power was recently switched off. t - Status Your boiler is simply reheating its internal hot water tank because the power was recently turned off and then back on.

Avoid the next call-out bill

Monthly cover means no unexpected bills when your boiler breaks down.

Approved partner
Domestic Appliance Guard
Unlimited call-outs, 24/7 helpline, no price-hike promise
Get a quote →

Affiliate links. We may earn a commission at no extra cost to you.