Baxi EcoBlue System Fault codes & diagnostics

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

System Natural Gas 12-32 kW 2015 onwards Discontinued
GC Numbers 41-070-2341-070-2441-070-2541-070-2641-070-2741-470-28

Replaced by: Baxi 600 System

Download the Baxi EcoBlue System manual The official installation & service manual (PDF) — the exact document these fault codes were verified against. PDF

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.
2 Emergency 29 High 1 Medium 4 Low
Versions & GC numbers

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
41-470-28 Ecoblue 32 System ErP 2015–present
Just want the most common Baxi EcoBlue System faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 36 documented codes

Tap any card for details

LED / flash-pattern codes
1 red flash

Your boiler has detected that it is getting too hot or that water isn't moving through the system correctly, causing it to shut down for safety.

High DIY-safe £120-250

What to check first

  1. Check that your radiator valves are open
  2. Ensure your system water pressure is between 1 and 1.5 bar on the gauge
  3. Reset the boiler by turning the selector switch to 'R' for five seconds

Parts commonly replaced

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

Related codes

Full explanation for 1 red flash
2 red flashes

Your boiler has become too hot and has shut itself down as a safety precaution to prevent damage.

High DIY-safe £100-£350

What to check first

  1. Check that your radiator valves are open and not turned to zero.
  2. Ensure your system water pressure is between 1 and 1.5 bar on the gauge.
  3. Turn the selector switch to the reset position for five seconds and then back to 'onn'.

Parts commonly replaced

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

Related codes

Full explanation for 2 red flashes
3 green flashes

Your boiler has briefly lost its flame and is trying to restart itself, which is often a temporary glitch that might resolve without any action.

Low DIY-safe £100-250

What to check first

  1. Monitor the boiler to see if it clears the fault and restarts automatically
  2. If the fault persists and turns into a solid red light, try a manual reset
  3. Check that your gas pre-payment meter (if applicable) has credit

Parts commonly replaced

  • Flame sensing electrode
  • Ignition lead
  • Gas valve

Related codes

Full explanation for 3 green flashes
3 red flashes

Your boiler has tried to light itself several times but cannot establish a flame, meaning you will have no heating or hot water until it is reset or repaired.

High DIY-safe £120-280

What to check first

  1. Check if other gas appliances in your home, like a hob, are working to ensure gas is reaching the property
  2. Check that your gas meter has credit if you use a pre-payment system
  3. Press and hold the reset button for five seconds to see if the boiler restarts

Parts commonly replaced

  • Ignition Electrode
  • Gas Valve
  • Flame Sensing Lead
  • Printed Circuit Board (PCB)
Full explanation for 3 red flashes
4 green flashes

Your boiler is having a temporary 'handshake' issue between its internal electronic brains, but it should fix itself automatically.

Low DIY-safe £0-120

What to check first

  1. Wait for the boiler to self-reset as this is often a temporary glitch
  2. If the flashing continues, turn the selector switch to 'Reset' for five seconds
  3. Monitor the boiler to see if the green flashes return

Parts commonly replaced

  • None (usually self-correcting)
  • Printed Circuit Board (PCB)

Related codes

Full explanation for 4 green flashes
4 red flashes

Your boiler's fan is not spinning or communicating correctly with the system, preventing the boiler from starting safely.

High Engineer only £250-£450

Parts commonly replaced

  • Fan assembly
  • Printed Circuit Board (PCB)
  • Wiring harness
Full explanation for 4 red flashes
5 green flashes

Your boiler has experienced a brief digital hiccup or settings error and is attempting to fix itself automatically.

Low DIY-safe £0-350

What to check first

  1. Wait for the boiler to complete its automatic self-reset process
  2. Monitor the display to see if the flashing stops naturally
  3. If the flashing continues for more than 10 minutes, try turning the boiler off and back on at the fused spur switch

Parts commonly replaced

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

Related codes

Full explanation for 5 green flashes
5 red flashes

Your boiler's internal memory chip has developed a communication fault, meaning the control board can no longer read its essential settings.

High Engineer only £120-250

Parts commonly replaced

  • Parameter Storage Unit (PSU)
  • Printed Circuit Board (PCB)
Full explanation for 5 red flashes
6 green flashes

Your boiler has encountered a minor glitch and is attempting to restart itself automatically without you needing to do anything.

Low DIY-safe £0-120

What to check first

  1. Wait up to 15 minutes for the boiler to complete its self-reset process
  2. Ensure the boiler's electrical supply is stable and not fluctuating
  3. Turn the selector switch to 'Reset' and back to 'On' if the light continues to flash

Parts commonly replaced

  • No parts usually required
  • Control PCB
Full explanation for 6 green flashes
6 red flashes

Your boiler has detected an internal communication or unexpected component fault and has stopped working as a safety precaution.

High DIY-safe £100-£350

What to check first

  1. Turn the selector switch to the 'Reset' position and hold for 5 seconds.
  2. Release the switch and wait for the boiler to attempt to restart.
  3. Ensure your gas supply is active and your credit meter (if applicable) has funds.

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Wiring harness
  • Gas Valve
Full explanation for 6 red flashes
Digital codes
08

Your boiler's electronic brain is experiencing an internal communication error that is preventing it from operating correctly.

High Engineer only £150-300

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Wiring harness
Full explanation for 08
20

Your boiler has lost the ability to accurately measure the temperature of the water circulating through your heating system, so it has shut down to prevent overheating.

High Engineer only £120-200

Parts commonly replaced

  • Central Heating NTC sensor
  • Wiring harness

Related codes

Full explanation for 20
28

Your boiler has detected a faulty sensor that monitors the temperature of the exhaust fumes, causing it to shut down for safety reasons.

High Engineer only £150-250

Parts commonly replaced

  • Flue NTC sensor
  • Wiring harness

Related codes

Full explanation for 28
40

Your boiler is struggling to accurately measure the temperature of the water returning to it, so it has stopped operating to stay on the safe side.

High Engineer only £120-200

Parts commonly replaced

  • Return NTC thermistor sensor
  • Wiring harness

Related codes

Full explanation for 40
109

Your boiler is struggling to pump water around your heating system effectively, so it has stopped working to prevent itself from overheating.

High Engineer only £150-350

Parts commonly replaced

  • Central heating pump
  • System filter
  • Diverter valve

Related codes

Full explanation for 109
109 R

Your boiler is struggling to pump water around your heating system effectively, so it has shut down to protect itself from overheating.

High Engineer only £150-300

Parts commonly replaced

  • Circulation Pump
  • System Filter
  • Diverter Valve

Related codes

Full explanation for 109 R
110

Your boiler has detected that it is overheating and has shut itself down to prevent damage because it cannot circulate water properly.

High DIY-safe £180-350

What to check first

  1. Turn off the boiler and allow it to cool down completely.
  2. Use a radiator key to bleed all radiators to remove any trapped air.
  3. Check the boiler pressure gauge and top it up to 1.5 bar if it has dropped.
  4. Turn the boiler back on and press the 'Reset' button.

Parts commonly replaced

  • Central heating pump
  • Safety thermostat
  • PCB
Full explanation for 110
110 R

Your boiler has detected that it is overheating and has shut itself down to prevent damage, likely because the water inside isn't circulating properly.

High Engineer only £150-300

Parts commonly replaced

  • Circulating pump
  • Safety overheat thermostat
  • Central heating sensor

Related codes

Full explanation for 110 R
111

Your boiler has detected that it is getting too hot and has automatically shut down to prevent damage or dangerous overheating.

High Engineer only £120-250

Parts commonly replaced

  • Safety Thermostat
  • System Pump
  • Diverter Valve
  • Heat Exchanger

Related codes

Full explanation for 111
111 R

Your boiler has detected that it is overheating and has automatically switched itself off to prevent damage.

High Engineer only £150-300

Parts commonly replaced

  • Pump
  • Diverter valve
  • Heat exchanger
  • Safety thermostat
Full explanation for 111 R
Showing 21–30 of 36
117

Your boiler's water pressure is currently too high, which has caused it to stop working as a safety precaution.

Medium DIY-safe £80-120

What to check first

  1. Locate a radiator in your home, preferably one upstairs.
  2. Place a cloth or small container under the radiator bleed valve.
  3. Use a radiator bleed key to slowly release a small amount of water until the pressure gauge on the front of your boiler drops into the green zone (usually between 1 and 1.5 bar).
  4. Once the pressure is correct, tighten the bleed valve securely.

Parts commonly replaced

  • Pressure relief valve
  • Expansion vessel
  • Filling loop valve

Related codes

Full explanation for 117
118

Your boiler has stopped working because the water pressure inside the heating system has dropped too low to operate safely.

High DIY-safe £80-150

What to check first

  1. Locate the external filling loop, which is a small silver flexible hose connecting two pipes near the boiler.
  2. Open the valves at both ends of the hose to allow water into the system until the pressure gauge reads between 1.0 and 1.5 bar.
  3. Close both valves tightly and ensure the hose is disconnected if required by your specific setup.

Parts commonly replaced

  • Filling loop
  • Pressure relief valve
  • Pressure sensor

Related codes

Full explanation for 118
125

Your boiler has detected that hot water is not flowing around your heating system correctly, which is causing it to shut down to prevent overheating.

High DIY-safe £150-350

What to check first

  1. Check that your system pressure is between 1 and 1.5 bar on the pressure gauge
  2. Ensure all radiator valves and isolation valves under the boiler are fully open
  3. Bleed your radiators to remove any trapped air pockets

Parts commonly replaced

  • Central heating pump
  • Diverter valve
  • System filter
Full explanation for 125
125 R

Your boiler has detected that hot water is not circulating properly around your heating system, so it has turned itself off to prevent overheating.

High Engineer only £150-350

Parts commonly replaced

  • Central heating pump
  • Diverter valve
  • Filter/System blockage
Full explanation for 125 R
128

Your boiler has attempted to start but failed to detect a flame, causing it to stop operating to ensure your safety.

High DIY-safe £120-250

What to check first

  1. Check that your gas pre-pay meter has credit
  2. Ensure other gas appliances in your home are working to confirm gas supply
  3. Press the 'Reset' button for five seconds

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Printed Circuit Board (PCB)
Full explanation for 128
130

Your boiler has detected that the temperature in the exhaust flue is too high, causing it to shut down for safety reasons.

Emergency Engineer only £150-300

Parts commonly replaced

  • Flue sensor
  • NTC thermistor
  • PCB
Full explanation for 130
133

Your boiler has attempted to start but could not light the internal flame, so it has shut down to prevent gas from building up.

High DIY-safe £120-250

What to check first

  1. Check that your gas supply is turned on and you have credit on your meter.
  2. During freezing weather, check if your external white plastic condensate pipe is frozen and thaw it with warm water.
  3. Press the Reset button for five seconds.

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Printed Circuit Board
Full explanation for 133
133 R

Your boiler has stopped working because it cannot light the flame required to produce heat or hot water.

High Engineer only £120-£250

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Circuit board (PCB)
  • Flame rectification probe
Full explanation for 133 R
151

Your boiler is trying to start but the flame won't stay lit, meaning your heating and hot water will not work.

High Engineer only £120-250

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Flame rectification probe
Full explanation for 151
151 R

Your boiler has attempted to ignite several times but has failed to detect a flame, causing it to shut down for safety.

High Engineer only £120-250

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Printed circuit board
Full explanation for 151 R
Showing 31–36 of 36
160

Your boiler's air circulation system has stopped working properly, preventing it from igniting safely.

High Engineer only £250-450

Parts commonly replaced

  • Fan assembly
  • Wiring harness
  • Control PCB
Full explanation for 160
160 R

Your boiler has detected that the internal fan responsible for safely venting exhaust gases is not working correctly, causing it to shut down for safety reasons.

High Engineer only £250-450

Parts commonly replaced

  • Fan assembly
  • Printed Circuit Board (PCB)
  • Wiring harness
Full explanation for 160 R
162

Your boiler has detected an issue with how it clears exhaust gases or brings in fresh air, preventing it from firing up for safety.

High Engineer only £120-£250

Parts commonly replaced

  • Air Pressure Switch
  • Venturi tube
  • Fan
Full explanation for 162
321

Your boiler has identified a problem with the temperature sensor, which is preventing it from safely heating your water.

High Engineer only £120-220

Parts commonly replaced

  • NTC Temperature Sensor
  • Wiring harness
Full explanation for 321
384

Your boiler has detected what it thinks is a flame inside the unit when the gas is supposed to be turned off, so it has shut down for safety.

Emergency Engineer only £150-300

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Flame sensing electrode
Full explanation for 384
E118

Your boiler has stopped working because the water pressure inside the heating system has dropped below the required level.

High DIY-safe £80-120

What to check first

  1. Locate the filling loop (usually a silver braided hose with one or two valves) connected to the boiler pipework.
  2. Gradually open the valve(s) to allow cold mains water to enter the system until the pressure gauge on the front of the boiler reads between 1.0 and 1.5 bar.
  3. Carefully close the valve(s) tightly to ensure no further water enters and the boiler restarts automatically.

Parts commonly replaced

  • Pressure relief valve
  • Expansion vessel
  • Filling loop
Full explanation for E118
Status & diagnostic codes

18 operating states & engineer diagnostics

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

1 green flash Status Your boiler has reached the correct temperature and is simply taking a natural rest; it is working exactly as it should. 01 Status Your boiler has detected that the water inside the heating system has become dangerously hot or is failing to move around the pipes properly. 02 Diagnostic Your boiler is having trouble communicating with the outdoor sensor that measures the air temperature, which may affect how efficiently your heating responds to weather changes. 03 Diagnostic Your boiler is struggling to detect the temperature of your hot water cylinder, preventing it from heating your water correctly. 04 Diagnostic Your boiler has detected an issue with the sensor that tracks the temperature of your water, which usually prevents the system from heating it correctly. 05 Diagnostic Your boiler has detected that the water pressure level inside the heating system has dropped too low for it to operate safely. 06 Diagnostic Your boiler has detected that the water returning from your radiators is at an unexpected temperature, causing it to pause for safety. 07 Diagnostic Your boiler has detected that the exhaust gases leaving the flue are hotter than they should be, so it has shut down to protect the system. 09 Diagnostic Your boiler has detected an issue with the temperature sensor reading, meaning it cannot safely monitor how hot the water inside is and has shut down to prevent damage. 10 Diagnostic Your boiler is unable to detect or properly control the temperature of the water circulating through your heating system. 12 Diagnostic Your boiler has failed to ignite because it cannot detect the flame, meaning it has safely shut itself down to prevent a gas buildup. 13 Diagnostic Your boiler is simply displaying a notification to let you know it has reached a certain number of hours of operation. 14 Diagnostic Your boiler is signalling an issue with the heating control system, which may be preventing your radiators from warming up as expected. 15 Diagnostic Your boiler is struggling to communicate with a secondary heating zone, such as an upstairs thermostat or a separate floor circuit. 16 Diagnostic Your boiler is signalling an issue while attempting to provide domestic hot water, likely due to a sensor or flow detection problem. 17 Diagnostic Your boiler is currently running normally and is successfully carrying out your heating or hot water request. 18 Diagnostic Your boiler is currently set to communicate with a solar water heating system, which is not a standard fault. 19 Diagnostic Your boiler has identified an internal electronic communication error that prevents it from starting up correctly.