Vokera Synergy System Fault codes & diagnostics

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

System Natural Gas 2024-present
GC Numbers 41-364-2241-364-2341-364-24
Download the Vokera Synergy 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 48 High 2 Medium 1 Low
Just want the most common Vokera Synergy System faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 53 documented codes

Tap any card for details

LED / flash-pattern codes
flashing bar value

The pressure inside your boiler is too high, which means the system has become overfilled with water.

Emergency DIY-safe £80-200

What to check first

  1. Locate the external filling loop valves (braided hose) and ensure they are tightly closed.
  2. Carefully bleed a radiator using a radiator key to release water until the pressure gauge returns to between 1.0 and 1.5 bar.
  3. Monitor the pressure gauge to ensure it stays stable and does not rise again.

Parts commonly replaced

  • Filling loop valve
  • Expansion vessel re-pressurisation
  • Pressure relief valve (PRV)

Related codes

Full explanation for flashing bar value
Digital codes
COM

The main computer boards inside your boiler have stopped talking to each other, causing the system to shut down for safety.

High Engineer only £180-450

Parts commonly replaced

  • Main PCB
  • Display PCB
  • Communication Wiring Harness

Related codes

Full explanation for COM
E010

Your boiler has failed to light or stay lit, meaning your heating and hot water have stopped working to keep the appliance safe.

High DIY-safe £100-350

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 if your gas meter has credit (if using a prepayment meter)
  3. Turn the mode selector switch to the 'OFF/RESET' position, wait five seconds, then turn it back to 'ON'

Parts commonly replaced

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

Related codes

Full explanation for E010
E011

Your boiler detects a flame when there should not be one, causing it to shut down for safety.

High Engineer only £120-280

Parts commonly replaced

  • Ionisation probe
  • Gas valve
  • Printed Circuit Board (PCB)

Related codes

Full explanation for E011
E012

Your boiler has stopped working because it has tried to light several times but the flame keeps going out.

High DIY-safe £120-280

What to check first

  1. Check that your gas supply is turned on at the meter
  2. Check if other gas appliances, like a hob, are working correctly
  3. Perform a reset by turning the mode selector dial to 'OFF/RESET' and then back to its original position

Parts commonly replaced

  • Ignition Electrode
  • Flame Sensing Probe
  • Gas Valve

Related codes

Full explanation for E012
E013

Your boiler's internal computer has failed a self-diagnostic check and cannot operate for safety reasons.

High Engineer only £250-£450

Parts commonly replaced

  • Main Printed Circuit Board (PCB)
  • Wiring Harness

Related codes

Full explanation for E013
E014

Your boiler is failing to confirm that a flame has been lit safely, so it has shut down as a precaution.

High Engineer only £120-£350

Parts commonly replaced

  • Flame sensing electrode
  • Ignition lead
  • PCB

Related codes

Full explanation for E014
E015

Your boiler has failed an internal safety test related to the flame detection system and cannot start for safety reasons.

High Engineer only £120-£350

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Ionisation Electrode
  • Wiring Harness

Related codes

Full explanation for E015
E020

Your boiler has shut down because it has detected that the internal water temperature has become too hot.

High DIY-safe £90-180

What to check first

  1. Check that your radiator valves are open and not turned to zero
  2. Turn the boiler mode selector to 'OFF' for 10 seconds, then back to the 'ON' position to reset
  3. Ensure your system pressure is between 1.0 and 1.5 bar on the pressure gauge

Parts commonly replaced

  • Limit Thermostat (High Limit Sensor)
  • Circulation Pump
  • NTC Temperature Sensor

Related codes

Full explanation for E020
E021

Your boiler has stopped working because its internal computer has detected a problem with how it manages the gas flow.

High Engineer only £180-350

Parts commonly replaced

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

Related codes

Full explanation for E021
Showing 11–20 of 53
E030

Your boiler has detected a problem with its internal fan system, which means it cannot safely move gases out of the flue and has shut down as a precaution.

High Engineer only £220-450

Parts commonly replaced

  • Fan assembly
  • Printed Circuit Board (PCB)
  • Venturi tube

Related codes

Full explanation for E030
E031

Your boiler has stopped working because the fan, which safely pushes exhaust fumes outside, has encountered a physical obstruction or has stopped spinning correctly.

High Engineer only £280-450

Parts commonly replaced

  • Fan assembly
  • Venturi tube
  • Air pressure switch

Related codes

Full explanation for E031
E032

The main component that blows air through your boiler has stopped spinning or is struggling to move, causing the system to shut down for safety.

High Engineer only £240-£450

Parts commonly replaced

  • Fan Assembly
  • Main PCB
  • Venturi Tube

Related codes

Full explanation for E032
E033

The fan that moves waste gases out of your boiler has stopped working properly, preventing the boiler from firing up for safety.

High Engineer only £250-£450

Parts commonly replaced

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

Related codes

Full explanation for E033
E034

Your boiler has detected a blockage or a technical issue within the flue pipe or air intake system that is preventing it from starting up safely.

High Engineer only £120-£350

Parts commonly replaced

  • Fan assembly
  • Air pressure switch
  • Flue seals
  • Venture tube

Related codes

Full explanation for E034
E035

Your boiler has detected an issue with how exhaust gases are being cleared, which is preventing it from running safely.

High Engineer only £100-280

Parts commonly replaced

  • Flue assembly
  • Fan
  • Air pressure switch
  • Venturi tube

Related codes

Full explanation for E035
E036

Your boiler is struggling to push waste gases out through the exhaust pipe, often due to a blockage or a component failure in the flue system.

High Engineer only £120-£350

Parts commonly replaced

  • Flue fan
  • Air pressure switch
  • Flue terminal

Related codes

Full explanation for E036
E037

Your boiler is struggling to maintain a stable flame during low-power operation, which may cause it to shut down for safety.

High Engineer only £120-350

Parts commonly replaced

  • Ionisation electrode
  • Gas valve
  • Burner gasket

Related codes

Full explanation for E037
E038

Your boiler is struggling to burn gas correctly when running at full power, causing it to shut down for safety.

High Engineer only £120-350

Parts commonly replaced

  • Gas valve
  • Electrode set
  • Fan
  • Venturi

Related codes

Full explanation for E038
E039

Your boiler's internal computer has detected an unusual signal from the flame, causing the system to shut down for safety purposes.

High Engineer only £120-350

Parts commonly replaced

  • Flame sensing electrode
  • Ignition lead
  • Printed Circuit Board (PCB)

Related codes

Full explanation for E039
Showing 21–30 of 53
E040

Your boiler has detected that the water pressure is too low, meaning there isn't enough water inside the system for it to run safely.

High DIY-safe £0-120

What to check first

  1. Locate the external filling loop, which is a silver flexible pipe with two small valves.
  2. Slowly open both valves until you hear water entering the system and watch the pressure gauge.
  3. Close both valves tightly once the pressure gauge reaches between 1.0 and 1.5 bar.

Parts commonly replaced

  • Filling loop
  • Expansion vessel
  • Pressure sensor

Related codes

Full explanation for E040
E041

The water pressure inside your boiler is too low for it to operate safely, and the system needs to be topped up.

High DIY-safe £0-120

What to check first

  1. Locate the external filling loop valves (usually underneath the boiler or nearby pipework)
  2. Slowly open both valves to allow water into the system
  3. Close both valves once the pressure gauge reaches between 1.0 and 1.5 bar

Parts commonly replaced

  • Filling loop
  • Expansion vessel
  • Pressure sensor

Related codes

Full explanation for E041
E042

Your boiler has stopped working because it cannot accurately detect if there is enough water pressure in the system to operate safely.

High Engineer only £130-220

Parts commonly replaced

  • Water pressure transducer
  • Wiring harness
  • Low Water Cut Off (LWCO) sensor

Related codes

Full explanation for E042
E050

Your boiler has detected a blockage or a fault in the flue pipe that is preventing exhaust fumes from escaping safely while the system is running at low power.

Emergency Engineer only £150-450

Parts commonly replaced

  • Flue fan
  • Air pressure switch
  • Flue ducting

Related codes

Full explanation for E050
E051

Your boiler has detected an issue with how exhaust gases are being cleared through the flue while running at high power.

High Engineer only £150-450

Parts commonly replaced

  • Fan assembly
  • Flue terminal
  • Venturi tube
  • Printed Circuit Board (PCB)

Related codes

Full explanation for E051
E052

Your boiler's internal computer has detected an electrical fault within its circuit board that it cannot correct itself.

High Engineer only £250-£450

Parts commonly replaced

  • Main Printed Circuit Board (PCB)

Related codes

Full explanation for E052
E055

Your boiler's main internal computer has lost contact with the fan that manages exhaust gases, forcing the system to shut down for safety.

High Engineer only £250-450

Parts commonly replaced

  • Modulating Fan
  • Main Control Board (PCB)
  • Wiring loom connectors

Related codes

Full explanation for E055
E056

Your boiler's internal computer parts have stopped talking to each other, meaning the unit cannot function or follow instructions.

High Engineer only £250-450

Parts commonly replaced

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

Related codes

Full explanation for E056
E060

Your boiler's computer system is currently confused and does not know how to correctly control your heating and hot water.

High Engineer only £120-250

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Configuration plug

Related codes

Full explanation for E060
E065

Your boiler's electronic control system has encountered an internal communication error and cannot safely manage the heating process.

High Engineer only £180-350

Parts commonly replaced

  • Main Printed Circuit Board (PCB)
  • Wiring Loom

Related codes

Full explanation for E065
Showing 31–40 of 53
E070

Your boiler has detected a sensor problem that monitors the temperature for your central heating, preventing the system from warming up your home.

High Engineer only £90-160

Parts commonly replaced

  • NTC Temperature Sensor
  • Wiring harness

Related codes

Full explanation for E070
E071

Your boiler has detected that the water in your central heating system is getting too hot, causing it to shut down for safety.

High DIY-safe £120-250

What to check first

  1. Check that all radiator valves are fully open
  2. Ensure the pressure gauge is between 1 and 1.5 bar
  3. Switch the boiler off and back on again to attempt a reset

Parts commonly replaced

  • CH NTC Temperature Sensor
  • Circulation Pump
  • Main Heat Exchanger (Descaling)

Related codes

Full explanation for E071
E072

Your boiler has detected that the water temperature leaving the unit is significantly different from the water returning to it, suggesting a circulation problem.

High DIY-safe £120-£350

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 on the gauge
  3. Gently bleed your radiators to remove any trapped air pockets

Parts commonly replaced

  • Circulation Pump
  • Temperature NTC Sensors
  • Main Heat Exchanger (Flushing)

Related codes

Full explanation for E072
E075

Your boiler is struggling to open an internal valve correctly, which is preventing the system from heating your home or water properly.

High Engineer only £140-£280

Parts commonly replaced

  • Three-way valve
  • Diverter valve motor
  • Main PCB

Related codes

Full explanation for E075
E077

Your boiler has detected a fault with the sensor that controls the temperature for your main heating circuit.

High Engineer only £100-£190

Parts commonly replaced

  • Main zone water thermostat (NTC sensor)
  • Wiring harness
  • Control board

Related codes

Full explanation for E077
E080

The boiler's sensor that monitors the temperature of the water returning from your radiators has developed a technical fault, causing the system to stop working for safety.

High Engineer only £90-160

Parts commonly replaced

  • Return NTC thermistor probe
  • Wiring harness
  • Main PCB

Related codes

Full explanation for E080
E081

Your boiler has shut down because the water returning from your radiators has become too hot, usually due to a lack of water flow through the system.

High DIY-safe £120-280

What to check first

  1. Check that your radiator valves are open to ensure water can move freely.
  2. Verify that the boiler pressure is between 1.0 and 1.5 bar on the gauge.
  3. Try resetting the boiler using the mode selector dial.

Parts commonly replaced

  • Return NTC Thermistor
  • Circulation Pump
  • Main Heat Exchanger (Flushing)

Related codes

Full explanation for E081
E082

Your boiler has detected that the water isn't circulating correctly through the system, meaning the difference in temperature between the water leaving and returning is too high.

High DIY-safe £120-350

What to check first

  1. Check that all radiator valves (TRVs) are fully open to allow water to flow.
  2. Ensure the central heating system pressure is between 1.0 and 1.5 bar on the gauge.
  3. Bleed any trapped air from your radiators using a radiator key.

Parts commonly replaced

  • Circulation pump
  • Flow/Return thermistors
  • Main heat exchanger (flushing/cleaning)

Related codes

Full explanation for E082
E088

Your boiler has detected an internal electrical communication error between its main control boards, preventing it from starting up correctly.

High Engineer only £180-450

Parts commonly replaced

  • Main PCB
  • Display Interface PCB
  • Wiring Harness

Related codes

Full explanation for E088
E090

Your boiler has detected an issue with the sensor that monitors the temperature of the exhaust gases, causing the system to shut down for safety.

High Engineer only £120-£220

Parts commonly replaced

  • Exhaust thermistor (NTC probe)
  • Wiring harness
  • Main PCB

Related codes

Full explanation for E090
Showing 41–50 of 53
E091

Your boiler has detected that the main heating component is becoming blocked with debris or limescale and needs a professional service.

Medium Engineer only £120-250

Parts commonly replaced

  • Primary heat exchanger
  • Main burner gasket
  • Seals

Related codes

Full explanation for E091
E092

Your boiler has failed to complete its internal safety and efficiency set-up, meaning it cannot verify that it is burning gas correctly.

High Engineer only £120-350

Parts commonly replaced

  • Gas Valve
  • Flame Sensing Electrode
  • Main Signal Cable
  • Printed Circuit Board (PCB)

Related codes

Full explanation for E092
E093

Your boiler has tried and failed to adjust its own combustion settings too many times and has locked itself out for safety.

High Engineer only £120-350

Parts commonly replaced

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

Related codes

Full explanation for E093
E094

Your boiler has detected an issue with the quality of the combustion gas and has shut down as a safety precaution.

High Engineer only £140-350

Parts commonly replaced

  • Lambda sensor
  • Gas valve
  • Electrode

Related codes

Full explanation for E094
E095

Your boiler has failed its internal self-tuning process and has locked out to ensure it doesn't burn gas inefficiently.

High Engineer only £100-£350

Parts commonly replaced

  • Ionisation Electrode
  • Gas Valve
  • Printed Circuit Board (PCB)

Related codes

Full explanation for E095
E096

Your boiler has shut down because it has detected an issue with the air and gas mixture required for safe combustion.

High Engineer only £180-450

Parts commonly replaced

  • Lambda sensor
  • Gas valve
  • Main PCB

Related codes

Full explanation for E096
E097

The boiler has detected an internal logic error during its self-test and has stopped working to prevent damage.

High Engineer only £250-500

Parts commonly replaced

  • Main PCB
  • Internal wiring harness

Related codes

Full explanation for E097
E098

Your boiler has encountered an internal electronic communication error that prevents it from starting correctly.

High Engineer only £180-£450

Parts commonly replaced

  • Main Printed Circuit Board (PCB)
  • Internal wiring harness

Related codes

Full explanation for E098
E099

Your boiler has been manually reset too many times in a short period and has locked itself as a safety precaution.

High DIY-safe £0-120

What to check first

  1. Turn off the electrical power supply to the boiler at the fused spur switch.
  2. Wait for approximately 30 seconds.
  3. Turn the power back on to clear the software lock.

Parts commonly replaced

  • None (Software reset)
  • Printed Circuit Board (PCB) if fault persists

Related codes

Full explanation for E099
FIL

Your boiler has detected that the water pressure in the heating system is too low to operate safely.

High DIY-safe £0-120

What to check first

  1. Locate the external filling loop (usually a silver flexible hose) underneath or near the boiler.
  2. Slowly open the valve or valves on the filling loop to allow water into the system.
  3. Monitor the pressure gauge and close the valves once the needle reaches approximately 1.5 bar, then restart the boiler.

Parts commonly replaced

  • Filling loop
  • Expansion vessel
  • Pressure relief valve

Related codes

Full explanation for FIL
Showing 51–53 of 53
FWER

Your boiler's internal computer chips are struggling to talk to each other because their software versions do not match.

High Engineer only £180-450

Parts commonly replaced

  • Main Printed Circuit Board (PCB)
  • Interface Display Board

Related codes

Full explanation for FWER
OBCD

Your boiler's internal computer clock has developed a fault, which means it can no longer keep track of its timing functions.

Medium Engineer only £250-450

Parts commonly replaced

  • Main Printed Circuit Board (PCB)

Related codes

Full explanation for OBCD
SFS

Your boiler is not broken, but it has reached its scheduled maintenance interval and requires a professional service to ensure it continues to work safely and efficiently.

Low Engineer only £80-£120

Parts commonly replaced

  • None - standard service items only
  • Burner seal
  • Electrodes

Related codes

Full explanation for SFS
Status & diagnostic codes

1 operating states & engineer diagnostics

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

CFS Diagnostic Your boiler has reached its preset service interval or has a non-critical fault and requires a professional maintenance check-up.
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