Worcester Bosch 1000 Fault codes & diagnostics

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

Combi Natural Gas 24-30 kW 2023-present

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Each cell = one fault code. Hover to identify.
9 Emergency 82 High 4 Medium 14 Low

All 109 documented codes

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203

Your boiler is perfectly healthy and simply waiting for a signal from your thermostat to turn on the heating or hot water.

Low DIY-safe

What to check first

  1. Turn up your room thermostat or smart controller settings
  2. Check that your hot water timer or programmer is set to 'On'
  3. Wait for a few minutes to see if the boiler fires up once a heat request is sent
204

Your boiler has detected that the water inside the unit is getting hotter than the temperature setting, so it has purposefully turned itself off to prevent overheating.

High Engineer only £150-300

Parts commonly replaced

  • NTC temperature sensor
  • Primary heat exchanger
  • Circulating pump

Related codes

208

Your boiler has been accidentally switched into a testing mode used by engineers to check emissions, which prevents it from heating your home normally.

Low DIY-safe

What to check first

  1. Locate the chimney sweep button on your boiler's front control panel.
  2. Press and hold the chimney sweep button for approximately 5 seconds.
  3. Wait for the display to return to the standard temperature reading and ensure the boiler resumes normal operation.
213

Your boiler has detected that the water leaving the boiler is much hotter than the water returning to it, suggesting the system is struggling to circulate heat properly.

High Engineer only £150-300

Parts commonly replaced

  • Circulation pump
  • System filter
  • Diverter valve

Related codes

214

Your boiler has detected that the internal fan is not spinning as expected during start-up, so it has safely shut down to prevent unsafe operation.

High Engineer only £180-350

Parts commonly replaced

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

Related codes

219

Your boiler has detected that the water inside the unit has become dangerously hot, so it has safely shut itself down to prevent damage.

High Engineer only £150-300

Parts commonly replaced

  • Circulation pump
  • NTC temperature sensor
  • Heat exchanger

Related codes

223

Your boiler has lost the connection to one of its temperature sensors, meaning it cannot accurately measure how hot the water is and has stopped working as a safety precaution.

High Engineer only £120-200

Parts commonly replaced

  • NTC sensor wiring harness
  • Temperature sensor

Related codes

Showing 11–20 of 109
224

Your boiler has switched itself off because it has detected an unsafe rise in internal temperature and needs to be inspected by a professional.

High Engineer only £120-250

Parts commonly replaced

  • NTC temperature sensor
  • Primary heat exchanger
  • Pump

Related codes

227

Your boiler is attempting to start but is unable to detect a steady flame, so it has safely shut down to prevent gas from escaping.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Printed Circuit Board (PCB)

Related codes

228

Your boiler has detected a sensor error where it believes a flame is present when it isn't, and it has safely locked itself out to prevent any issues.

High Engineer only £150-300

Parts commonly replaced

  • Printed circuit board
  • Flame rectification probe

Related codes

229

Your boiler's flame has gone out while it was trying to heat your water, which means the boiler has safely shut itself down to prevent any issues.

High Engineer only £120-250

Parts commonly replaced

  • Electrodes
  • Gas valve
  • Gas pressure regulator
  • Printed circuit board

Related codes

232

Your boiler has been intentionally switched off or put into standby mode by an external device, such as a smart thermostat, a programmer, or a safety control system.

High Engineer only £90-180

Parts commonly replaced

  • External wiring
  • Heating programmer
  • Smart thermostat receiver

Related codes

233

Your boiler's computer is having trouble recognising its own internal settings, which is preventing it from starting up correctly.

High Engineer only £250-450

Parts commonly replaced

  • Main control board
  • Coding plug

Related codes

234

Your boiler is not detecting the electrical connection to the gas supply mechanism, meaning it cannot safely ignite to provide heating or hot water.

High Engineer only £150-250

Parts commonly replaced

  • Gas valve
  • Wiring harness
  • PCB

Related codes

235

Your boiler's internal computer is confused because its software settings don't match the specific model hardware installed.

High Engineer only £150-300

Parts commonly replaced

  • PCB
  • Programming Key

Related codes

237

Your boiler has detected a general internal communication failure, meaning it cannot safely operate its main control systems.

High Engineer only £150-300

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Wiring harness

Related codes

238

Your boiler's main control unit has identified an internal electronic error and has shut down to prevent potential damage.

High Engineer only £250-450

Parts commonly replaced

  • Main PCB
  • Wiring harness

Related codes

Showing 21–30 of 109
240

Your boiler has lost the signal from one of its internal temperature sensors, meaning it cannot correctly measure the heat of the water and has stopped running to stay safe.

High Engineer only £120-200

Parts commonly replaced

  • NTC Temperature Sensor
  • Wiring harness

Related codes

241

Your boiler has lost the connection to one of its temperature sensors, which is preventing it from working correctly.

High Engineer only £120-200

Parts commonly replaced

  • NTC Temperature Sensor
  • Wiring harness

Related codes

245

Your boiler's internal computer is receiving a signal that falls outside of its expected operating parameters, causing it to shut down for safety.

High Engineer only £150-350

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Wiring harness
  • Sensor module

Related codes

249

Your boiler's computer is experiencing a temporary processing glitch that is preventing it from starting up correctly.

High Engineer only £150-300

Parts commonly replaced

  • Main printed circuit board (PCB)
250

Your boiler's computer has encountered an internal error and needs a reset or a service technician to investigate the control system.

High Engineer only £150-300

Parts commonly replaced

  • Main PCB
  • Control Unit

Related codes

251

Your boiler's internal computer has detected a serious communication failure during its safety check, preventing it from starting up safely.

High Engineer only £250-450

Parts commonly replaced

  • Main control board (PCB)

Related codes

252

Your boiler's internal computer is experiencing a software memory error, preventing it from operating correctly.

High Engineer only £150-250

Parts commonly replaced

  • Main Control Board (PCB)

Related codes

253

Your boiler's internal computer is experiencing a memory error and cannot safely operate the system.

High Engineer only £250-450

Parts commonly replaced

  • Main printed circuit board (PCB)
  • Control unit

Related codes

254

Your boiler's internal computer is experiencing a memory error, meaning it has lost its stored settings and cannot safely manage its operations.

High Engineer only £250-450

Parts commonly replaced

  • Main Control Board
  • PCB
258

Your boiler's internal computer is experiencing a temporary software glitch and has shut down to prevent any unsafe operation.

High Engineer only £200-400

Parts commonly replaced

  • Main printed circuit board (PCB)
  • Control unit
Showing 31–40 of 109
259

Your boiler has detected an internal communication error with its main control unit that is preventing it from operating correctly.

High Engineer only £150-300

Parts commonly replaced

  • Printed Circuit Board (PCB)

Related codes

262

The boiler's internal computer is experiencing a temporary software glitch and cannot properly communicate with its internal systems.

High Engineer only £150-300

Parts commonly replaced

  • Main control board
  • PCB

Related codes

263

Your boiler's computer is having trouble starting up its internal system properly, which is preventing it from firing up.

High Engineer only £150-300

Parts commonly replaced

  • Printed Circuit Board (PCB)

Related codes

265

Your boiler is temporarily turning itself off because your radiators or taps aren't taking away the heat as fast as the boiler is producing it, often due to poor water flow.

Medium Engineer only £120-250

Parts commonly replaced

  • Central heating pump
  • System filter
  • Diverter valve

Related codes

268

Your boiler has detected an internal communication glitch during its self-test phase, which prevents it from firing up safely.

High Engineer only £150-300

Parts commonly replaced

  • Main control board (PCB)
  • Wiring harness

Related codes

269

Your boiler has detected that the flame is not burning as it should and has shut itself down to keep your home safe.

High Engineer only £150-300

Parts commonly replaced

  • Ionisation electrode
  • Ignition lead
  • Gas valve
  • Printed circuit board

Related codes

273

Your boiler has detected that the flame-making process has stopped, preventing your heating or hot water from working.

High Engineer only £150-300

Parts commonly replaced

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

Related codes

275

Your boiler has accidentally been left in a restricted diagnostic mode used by engineers during installation, meaning it cannot currently heat your home or water.

High Engineer only £80-150
278

Your boiler has detected an internal sensor failure and has stopped working completely to ensure safety.

High Engineer only £150-250

Parts commonly replaced

  • NTC Temperature Sensor
  • Control Module
Showing 41–50 of 109
284

Your boiler is having trouble managing the balance of air and gas required for safe combustion and has locked itself out to prevent potential issues.

High Engineer only £150-300

Parts commonly replaced

  • Gas valve
  • Gas valve harness

Related codes

285

Your boiler has detected that the water returning to it is much hotter than expected, suggesting heat isn't circulating properly through your radiators.

Medium Engineer only £120-250

Parts commonly replaced

  • NTC Sensor
  • Pump
  • Diverter Valve

Related codes

305

Your boiler has detected that it is running the hot water cycle too frequently and is temporarily pausing to prevent overheating or unnecessary wear.

Low Engineer only £100-250

Parts commonly replaced

  • NTC sensor
  • Flow sensor
  • Main printed circuit board

Related codes

306

Your boiler has detected that a flame is still present even though it has tried to turn the gas supply off, which indicates a potential safety control issue.

Emergency Engineer only £150-300

Parts commonly replaced

  • Gas valve
  • Printed Circuit Board (PCB)

Related codes

341

Your boiler is shutting down because the water inside is heating up much faster than it is moving, which often means there is an internal blockage or a pump issue.

High Engineer only £150-350

Parts commonly replaced

  • Central heating pump
  • System filter
  • Heat exchanger
347

Your boiler has detected that hot water is flowing the wrong way or the pipes are incorrectly connected, causing it to shut down to prevent damage.

High Engineer only £150-300

Parts commonly replaced

  • Flow/Return sensors
  • Pump
  • Diverter valve
351

Your boiler has lost the ability to read the temperature of the water inside it, so it has shut down to stay safe.

High Engineer only £120-220

Parts commonly replaced

  • NTC Temperature Sensor
  • Wiring harness

Related codes

353

Your boiler has detected an internal electronic error during a safety self-test and has shut itself down to prevent unsafe operation.

High Engineer only £150-300

Parts commonly replaced

  • Printed Circuit Board (PCB)
357

Your boiler is currently running a brief automatic test to clear any lingering gases from the internal system before it attempts to fire up again.

Low Engineer only

Parts commonly replaced

  • Flue fan
  • Air pressure switch
  • Venturi
Showing 51–60 of 109
360

Your boiler's internal computer chip is not communicating correctly with its main control board, which prevents the unit from starting safely.

High Engineer only £150-300

Parts commonly replaced

  • Code plug
  • Main printed circuit board

Related codes

362

Your boiler's computer is having trouble communicating with its internal memory, which prevents it from safely operating your heating and hot water.

High Engineer only £250-450

Parts commonly replaced

  • PCB (Printed Circuit Board)
  • Coding Plug

Related codes

363

Your boiler has detected that the flame is remaining active when it should have shut off, preventing it from starting safely.

Emergency Engineer only £180-350

Parts commonly replaced

  • Gas Valve
  • Printed Circuit Board (PCB)
  • Flame Rectification Probe

Related codes

364

Your boiler has detected that an internal valve responsible for controlling gas flow is not closing correctly, meaning it is unsafe to continue operating.

Emergency Engineer only £200-350

Parts commonly replaced

  • Gas valve assembly
  • Solenoid coil

Related codes

365

Your boiler has detected an internal gas valve fault, meaning it can no longer safely manage the flow of fuel to the burner, so it has shut down to protect your home.

Emergency Engineer only £250-400

Parts commonly replaced

  • Gas valve assembly
  • Wiring harness

Related codes

522

Your boiler is currently performing a routine self-check of its temperature sensors to ensure it is operating safely and accurately.

Low Engineer only

Parts commonly replaced

  • NTC Temperature Sensor
568

Your boiler is currently unable to read its own water pressure levels, which forces the system to shut down to prevent potential damage.

High Engineer only £150-250

Parts commonly replaced

  • Water pressure sensor
  • Wiring harness
578

Your boiler has detected a faulty sensor that monitors temperatures, meaning it cannot safely control its heat output and has shut down to protect itself.

High Engineer only £120-220

Parts commonly replaced

  • NTC Sensor
  • Wiring harness
604

Your boiler has detected an internal communication error and has safely shut itself down to prevent it from operating incorrectly.

High Engineer only £200-400

Parts commonly replaced

  • Main control board
  • Wiring harness
Showing 61–70 of 109
1010

Your boiler's electronic control system is failing to communicate with its internal components, meaning the boiler has stopped working to protect itself.

High Engineer only £150-350

Parts commonly replaced

  • Main printed circuit board (PCB)
  • Wiring harness or ribbon cable
1013

Your boiler has detected that the burner is running at its maximum capacity for too long, causing it to proactively shut down to prevent overheating.

High Engineer only £120-250

Parts commonly replaced

  • Heat exchanger
  • Flow sensor
  • System filter
1018

Your boiler is simply reminding you that it is due for its annual safety service.

Low Engineer only £90-130
1019

Your boiler has identified that the internal water pump is not the correct type for this specific model, which is preventing the system from operating correctly.

High Engineer only £250-450

Parts commonly replaced

  • Central heating pump
  • Printed Circuit Board

Related codes

1021

Your boiler is struggling to accurately detect the temperature of your hot water, which means it may fail to heat your water or work inconsistently.

Medium Engineer only £120-200

Parts commonly replaced

  • NTC temperature sensor
  • Wiring harness

Related codes

1023

Your boiler has been running for a very long period without a break and has automatically paused to prevent overheating.

Low DIY-safe

What to check first

  1. Switch the boiler off at the mains power supply
  2. Wait for 60 seconds to allow the system to reset
  3. Switch the power back on and observe if normal operation resumes

Related codes

1025

Your boiler is struggling to accurately monitor the temperature of the water returning to it, so it has stopped working to prevent potential overheating.

High Engineer only £150-250

Parts commonly replaced

  • Return temperature sensor (NTC sensor)
1068

Your boiler is struggling to read external data needed to adjust its settings, which may cause your heating to run less efficiently than usual.

Low Engineer only £120-200

Parts commonly replaced

  • External temperature sensor
  • Oxygen sensor (Lambda probe)
1073

Your boiler has detected a faulty electrical signal regarding how hot the water is inside the system and has stopped working to prevent damage.

High Engineer only £120-220

Parts commonly replaced

  • Flow NTC sensor
  • Wiring harness

Related codes

1074

Your boiler has lost the ability to measure the temperature of the water inside it, so it has safely shut itself down to prevent overheating.

High Engineer only £150-250

Parts commonly replaced

  • Flow temperature sensor
  • Wiring harness
Showing 71–80 of 109
2085

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

  • Main Control Board
  • Wiring harness
2207

Your boiler's water pump is failing to communicate correctly with the main control board, which means it cannot circulate water effectively to heat your home.

High Engineer only £250-450

Parts commonly replaced

  • Circulation pump
  • Wiring harness
  • Main control board
2908

Your boiler's main control computer is experiencing an internal error and cannot operate safely, meaning your heating and hot water will not work.

High Engineer only £250-450

Parts commonly replaced

  • Main Printed Circuit Board (PCB)
  • Control unit
2910

Your boiler has detected an issue with the pipework that vents exhaust gases outside, meaning it has safely shut itself down to prevent any harmful fumes building up indoors.

Emergency Engineer only £150-350

Parts commonly replaced

  • Flue duct seals
  • Pressure switch
  • Fan assembly
  • Flue terminal
2915

Your boiler's ventilation fan is continuing to run long after it should have finished cooling down, which often indicates an internal electronic fault.

Medium Engineer only £150-300

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Fan assembly

Related codes

2916

Your boiler has detected that the internal gas valve failed to close properly after it finished its last cycle, which could pose a safety risk.

Emergency Engineer only £200-350

Parts commonly replaced

  • Gas valve
  • Printed Circuit Board (PCB)
2920

Your boiler is failing to detect a flame, so it has safely shut itself down to prevent gas from building up.

Emergency Engineer only £180-350

Parts commonly replaced

  • Ionisation electrode
  • Main PCB
  • Gas valve

Related codes

2923

Your boiler has detected an issue with the valve that controls the gas supply, meaning it has safely shut itself down to prevent any risk.

Emergency Engineer only £250-450

Parts commonly replaced

  • Gas valve
  • Printed Circuit Board (PCB)

Related codes

2924

Your boiler has detected an issue with the fuel supply system, meaning it cannot confirm that gas is flowing correctly, so it has safely shut itself down.

Emergency Engineer only £150-300

Parts commonly replaced

  • Gas valve
  • Wiring harness
  • Main control board (PCB)

Related codes

2925

Your boiler is struggling to control the gas flow needed to heat your home, so it has safely shut itself down to prevent any issues.

High Engineer only £180-350

Parts commonly replaced

  • Gas valve
  • Main PCB

Related codes

Showing 81–90 of 109
2926

Your boiler has detected an issue with the control system that regulates the gas flow, meaning it has switched itself off to stay safe and is currently unable to provide heating or hot water.

High Engineer only £180-350

Parts commonly replaced

  • Gas valve
  • Printed Circuit Board (PCB)

Related codes

2927

Your boiler has stopped heating because the flame inside went out while it was trying to run.

High Engineer only £150-300

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Printed Circuit Board (PCB)

Related codes

2928

Your boiler has detected a communication error between its internal electronic brains, causing it to shut down for safety.

High Engineer only £150-300

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Wiring harness

Related codes

2930

Your boiler has detected an internal communication failure between its main computer and the main heating component, preventing it from starting safely.

High Engineer only £250-450

Parts commonly replaced

  • Main Control Board
  • Wiring Harness
  • Heat Exchanger Sensor
2931

The internal computer in your boiler has encountered a major software error and has stopped operating to prevent further damage.

High Engineer only £250-450

Parts commonly replaced

  • Main printed circuit board (PCB)
2940

Your boiler's electronic control system is not receiving the correct amount of electrical power, preventing it from starting safely.

High Engineer only £120-250

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Wiring harness
  • Power supply unit

Related codes

2946

Your boiler's internal computer is struggling to recognise the specific settings for your model, causing it to shut down for safety.

High Engineer only £150-250

Parts commonly replaced

  • Code plug
  • Printed Circuit Board (PCB)
2948

Your boiler is trying to start but is failing to stay on because it cannot detect a stable flame.

High Engineer only £150-300

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Flame rectification probe

Related codes

2949

Your boiler has attempted to ignite several times but is failing to stay lit, so it has shut down as a safety precaution.

High Engineer only £150-300

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Flame rectification probe

Related codes

2950

Your boiler is failing to light the internal flame needed to produce heat and hot water.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Control board

Related codes

Showing 91–100 of 109
2951

Your boiler is repeatedly trying to stay lit but failing, which means it will stop working to keep you safe.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Flame rectification probe

Related codes

2952

Your boiler is having trouble confirming that the burner is lit safely, so it has stopped working to prevent any potential risks.

High Engineer only £150-£300

Parts commonly replaced

  • Ignition electrode
  • PCB
  • Wiring harness

Related codes

2955

Your boiler has detected that the internal plumbing settings do not match the physical components installed, preventing it from functioning correctly.

High Engineer only £150-300

Parts commonly replaced

  • Main PCB
  • Hydraulic block

Related codes

2956

Your boiler has detected that water is not circulating correctly through its internal heating unit, preventing it from producing heat safely.

High Engineer only £150-300

Parts commonly replaced

  • Circulation pump
  • Diverter valve
  • Flow sensor

Related codes

2957

Your boiler has detected a temporary internal computer glitch that is preventing it from starting up correctly.

High Engineer only £150-300

Parts commonly replaced

  • Control board
  • PCB

Related codes

2958

Your boiler's internal computer is experiencing a communication error or failure and is unable to operate safely.

High Engineer only £250-450

Parts commonly replaced

  • Main printed circuit board (PCB)
  • Wiring harness

Related codes

2959

Your boiler's internal computer is experiencing a software or communication error and has safely shut itself down to prevent further issues.

High Engineer only £150-350

Parts commonly replaced

  • Main control board
  • Wiring harness

Related codes

2960

Your boiler's main control computer is experiencing a communication or internal processing error, causing it to shut down to prevent damage.

High Engineer only £250-450

Parts commonly replaced

  • Main PCB
  • Wiring harness
2961

Your boiler is unable to detect that its internal air fan is spinning, so it has safely shut itself down to prevent operation without proper ventilation.

High Engineer only £180-350

Parts commonly replaced

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

Related codes

2962

Your boiler has stopped working because the internal component responsible for clearing exhaust gases is not spinning, which prevents the unit from firing up safely.

High Engineer only £180-350

Parts commonly replaced

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

Related codes

Showing 101–109 of 109
2963

Your boiler has detected that a temperature sensor is sending inconsistent data, so it has safely shut itself down to prevent potential overheating.

High Engineer only £150-250

Parts commonly replaced

  • NTC temperature sensor
  • Wiring harness
  • Printed Circuit Board

Related codes

2964

Your boiler is struggling to pump water through its internal system effectively, which is likely preventing it from producing heat or hot water.

High Engineer only £150-350

Parts commonly replaced

  • Central heating pump
  • Diverter valve
  • Primary heat exchanger

Related codes

2965

Your boiler has detected that the water inside the unit is getting too hot, so it has safely shut itself down to prevent damage to your heating system.

High Engineer only £120-£250

Parts commonly replaced

  • NTC Temperature Sensor
  • Pump
  • Diverter Valve

Related codes

2966

Your boiler is shutting down because it is heating up much faster than the water can move through the system, often caused by a circulation blockage or a failing internal pump.

High Engineer only £180-350

Parts commonly replaced

  • Central heating pump
  • Diverter valve
  • System filter

Related codes

2972

Your boiler is struggling to work because the electricity supply coming from your home's wall socket or wiring is weaker than it needs to be.

High Engineer only £120-250

Parts commonly replaced

  • External fuse spur
  • Main printed circuit board (PCB)
  • Power supply cabling

Related codes

2973

Your boiler’s internal computer is experiencing a communication error or software glitch that is preventing it from operating correctly.

High Engineer only £200-450

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Control wiring harness

Related codes

2974

Your boiler's computer is experiencing an internal error and cannot operate correctly, which means you currently have no heating or hot water.

High Engineer only £200-400

Parts commonly replaced

  • Main printed circuit board (PCB)

Related codes

2980

Your boiler has flagged too many faults in a short time and has now locked itself to prevent damage, meaning it will no longer operate until a professional resets the system safely.

High Engineer only £120-300

Parts commonly replaced

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

Related codes

2981

Your boiler has switched itself off permanently because of repeated failed attempts to start, and it now requires a professional to safely unlock the system.

High Engineer only £120-250

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Printed circuit board

Related codes