Vokera Synergy Combi Fault codes & diagnostics

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

Combi Natural Gas 2024-present
GC Numbers 47-364-7647-364-7747-364-78
Download the Vokera Synergy Combi 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.
3 Emergency 43 High 1 Medium 1 Low
Just want the most common Vokera Synergy Combi faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 48 documented codes

Tap any card for details

LED / flash-pattern codes
flashing bar value

Your boiler has too much water pressure inside the system, which can cause leaks or safety valves to trigger.

Emergency DIY-safe £0-120

What to check first

  1. Check that the filling loop valves (under the boiler) are tightly closed.
  2. Turn off the boiler and wait for the radiators to cool down.
  3. Bleed a radiator using a radiator key to let out water until the pressure gauge returns to between 1 and 1.5 bar.

Parts commonly replaced

  • Filling loop valve
  • Expansion vessel
  • Pressure relief valve (PRV)

Related codes

Full explanation for flashing bar value
Digital codes
COM

Your boiler's internal computer has lost touch with its control system, meaning it can no longer send signals to heat your home or water.

High Engineer only £180-450

Parts commonly replaced

  • Main PCB
  • Display Interface PCB
  • Wiring Loom

Related codes

Full explanation for COM
E010

Your boiler has failed to light or maintain a flame, causing the system to shut down for safety.

High DIY-safe £100-350

What to check first

  1. Check if your home has other working gas appliances (like a hob) to ensure gas is reaching the property
  2. Check that your gas prepayment meter has credit
  3. Press and hold the 'R' or reset button for a few seconds to restart the ignition process

Parts commonly replaced

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

Related codes

Full explanation for E010
E011

Your boiler has detected a flame in the burner when there shouldn't be one, causing it to stop for safety.

High Engineer only £120-300

Parts commonly replaced

  • Flame sensing electrode
  • Gas valve
  • Main circuit board (PCB)

Related codes

Full explanation for E011
E012

Your boiler has tried to stay lit multiple times but the flame keeps going out, so it has shut down for safety.

High Engineer only £120-350

Parts commonly replaced

  • Ionisation electrode
  • Gas valve
  • Flue seals
  • Condensate trap

Related codes

Full explanation for E012
E013

The boiler's internal computer has detected a technical hardware failure during its startup checks and has shut down for safety.

High Engineer only £280-550

Parts commonly replaced

  • Main Control PCB
  • Display Interface Board

Related codes

Full explanation for E013
E014

Your boiler is struggling to confirm that a flame has been successfully lit, which prevents it from running for safety reasons.

High Engineer only £120-280

Parts commonly replaced

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

Related codes

Full explanation for E014
E015

Your boiler has failed a safety check related to how it detects the flame, meaning it cannot start up for your heating or hot water.

High Engineer only £140-£350

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Ignition Electrode
  • Flame Sensing Electrode

Related codes

Full explanation for E015
E020

Your boiler has switched itself off because it has detected it is getting too hot and needs to cool down for safety.

High DIY-safe £100-220

What to check first

  1. Ensure all radiator valves (TRVs) are turned to the highest setting
  2. Check that the system water pressure is between 1.0 and 1.5 bar on the gauge
  3. Allow the boiler to cool down and then press the 'Reset' button

Parts commonly replaced

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

Related codes

Full explanation for E020
E021

The boiler's internal computer has lost control over the flow of gas, causing the system to shut down for safety purposes.

High Engineer only £180-350

Parts commonly replaced

  • Gas Valve
  • Main PCB

Related codes

Full explanation for E021
Showing 11–20 of 48
E032

Your boiler has detected that the fan, which safely removes waste gases from the system, has stopped spinning or is blocked.

High Engineer only £250-450

Parts commonly replaced

  • Fan Assembly
  • Venturi Tube
  • Main PCB

Related codes

Full explanation for E032
E033

Your boiler has stopped working because the fan that helps push exhaust gases out of your home has broken or is spinning at the wrong speed.

High Engineer only £280-450

Parts commonly replaced

  • Fan assembly
  • Main circuit board (PCB)
  • Fan wiring harness

Related codes

Full explanation for E033
E034

Your boiler is struggling to clear air from the system before it starts up, which is usually caused by a blockage in the flue pipe or a technical fault with the internal fan.

High Engineer only £120-£350

Parts commonly replaced

  • Fan
  • Air Pressure Switch
  • Venturi Tube
  • Flue seals

Related codes

Full explanation for E034
E035

Your boiler is struggling to breathe properly because something is blocking the pipes that carry exhaust gases outside.

High Engineer only £100-280

Parts commonly replaced

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

Related codes

Full explanation for E035
E037

Your boiler is struggling to maintain a stable flame when running at a low power level, which is causing it to shut down for safety.

High Engineer only £100-£280

Parts commonly replaced

  • Ionisation Electrode
  • Gas Valve
  • Burner

Related codes

Full explanation for E037
E040

Your boiler has stopped working because the water pressure is too low and needs to be topped up.

High DIY-safe £0-120

What to check first

  1. Locate the metal braided filling loop underneath or near the boiler.
  2. Open the black taps on the filling loop slowly until you hear water entering the system.
  3. Close the taps once the pressure gauge on the boiler reaches between 1 and 1.5 bar.

Parts commonly replaced

  • Filling loop valves
  • Expansion vessel
  • Pressure sensor

Related codes

Full explanation for E040
E041

Your boiler has detected that the water pressure is getting low and needs to be topped up to continue working.

High DIY-safe £0-120

What to check first

  1. Locate the filling loop (usually a silver braided hose with small valves) underneath the boiler.
  2. Open the valves slowly until you hear water entering the system.
  3. Watch the pressure gauge and close the valves tightly once it reaches 1.5 bar.
  4. The error should clear automatically; if it has progressed to E040, you may need to press the Reset button.

Parts commonly replaced

  • Filling loop
  • Pressure sensor
  • Expansion vessel

Related codes

Full explanation for E041
E042

Your boiler's internal water pressure sensor is reporting a fault, which has caused the system to shut down to prevent damage.

High DIY-safe £120-£210

What to check first

  1. Check the pressure gauge on the front of the boiler; it should be between 1.0 and 1.5 bar.
  2. If the pressure is too low, use the filling loop valves to top up the water level.
  3. Restart the boiler by turning the mode selector switch to 'OFF/RESET' and then back to the desired position.

Parts commonly replaced

  • Water pressure transducer
  • Pressure switch
  • Wiring harness

Related codes

Full explanation for E042
E050

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

Emergency Engineer only £150-£450

Parts commonly replaced

  • Flue fan
  • Air pressure switch
  • Flue terminal
  • Main PCB

Related codes

Full explanation for E050
E051

Your boiler has detected a blockage or restriction in the flue pipe that prevents exhaust fumes from escaping safely at high power.

Emergency Engineer only £120-350

Parts commonly replaced

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

Related codes

Full explanation for E051
Showing 21–30 of 48
E052

Your boiler's main control board has detected an internal electronic failure and can no longer operate your heating or hot water safely.

High Engineer only £250-£450

Parts commonly replaced

  • Main Printed Circuit Board (PCB)

Related codes

Full explanation for E052
E055

Your boiler's main control computer is unable to talk to the fan, which means the system cannot safely clear exhaust gases and will not start.

High Engineer only £180-450

Parts commonly replaced

  • Fan
  • Main PCB (Printed Circuit Board)
  • Wiring Harness

Related codes

Full explanation for E055
E056

Your boiler's internal computer brain is unable to talk to its control board, meaning the system cannot start or function safely.

High Engineer only £250-550

Parts commonly replaced

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

Related codes

Full explanation for E056
E060

Your boiler is having trouble measuring the temperature of your hot water, which means your taps and showers may not get warm.

High Engineer only £90-160

Parts commonly replaced

  • DHW NTC Thermistor
  • Connecting wiring harness

Related codes

Full explanation for E060
E065

Your boiler has detected an internal communication error with the main control system, meaning it cannot safely regulate the burner.

High Engineer only £180-450

Parts commonly replaced

  • Main Printed Circuit Board (PCB)
  • IMOD expansion Board
  • Wiring harness

Related codes

Full explanation for E065
E070

Your boiler's central heating sensor has stopped communicating correctly, meaning the system doesn't know the temperature of your radiators and has shut down as a precaution.

High Engineer only £90-160

Parts commonly replaced

  • Central Heating (CH) NTC thermistor probe
  • Wiring harness connectors

Related codes

Full explanation for E070
E071

Your boiler is shutting down because the water in the central heating circuit has reached an unsafely high temperature.

High DIY-safe £90-180

What to check first

  1. Ensure all radiator valves are fully open to allow water to circulate
  2. Check that the boiler pressure is between 1.0 and 1.5 bar on the pressure gauge
  3. If the pressure is low, top it up using the filling loop
  4. Try resetting the boiler using the control dial

Parts commonly replaced

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

Related codes

Full explanation for E071
E072

Your boiler has detected that the water temperature entering the system is too different from the temperature returning to it, suggesting the water isn't flowing through your pipes correctly.

High DIY-safe £120-350

What to check first

  1. Check that all radiator valves (TRVs) are fully open and not turned to zero
  2. Ensure the boiler pressure is between 1.0 and 1.5 bar on the pressure gauge
  3. Bleed any air out of your radiators and reset the boiler

Parts commonly replaced

  • Circulation Pump
  • Main Heat Exchanger
  • Flow/Return NTC Sensors

Related codes

Full explanation for E072
E075

Your boiler is struggling to open a gas valve properly, which is preventing the burner from lighting or staying on.

High Engineer only £180-350

Parts commonly replaced

  • Gas Valve
  • Printed Circuit Board (PCB)

Related codes

Full explanation for E075
E077

Your boiler has detected a problem with the temperature sensor that controls your main heating circuit, preventing it from managing the water temperature correctly.

High Engineer only £90-180

Parts commonly replaced

  • NTC Temperature Sensor
  • Wiring harness
  • Main PCB

Related codes

Full explanation for E077
Showing 31–40 of 48
E080

Your boiler has stopped working because a sensor that monitors the temperature of the water returning to the unit has developed a fault.

High Engineer only £120-190

Parts commonly replaced

  • Return NTC thermistor (temperature probe)
  • Wiring harness
  • Control board

Related codes

Full explanation for E080
E081

Your boiler has shut down because the water returning from your radiators has become too hot, which usually points to a circulation problem.

High DIY-safe £90-250

What to check first

  1. Check that all radiator valves (TRVs) are fully open
  2. Ensure the boiler pressure is between 1.0 and 1.5 bar on the gauge
  3. Try resetting the boiler using the control dial

Parts commonly replaced

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

Related codes

Full explanation for E081
E082

Your boiler has detected that the water is not flowing through the system correctly, causing a temperature imbalance between the pipes going out and coming back in.

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 and 1.5 bar on the pressure gauge.
  3. Reset the boiler using the control knob or button to see if the fault clears.

Parts commonly replaced

  • Circulation Pump
  • Thermistor (NTC Sensor)
  • Main Heat Exchanger (Cleaning/Flushing)

Related codes

Full explanation for E082
E088

Your boiler has detected an internal communication error between its main control boards, meaning the system cannot coordinate its functions correctly.

High Engineer only £180-350

Parts commonly replaced

  • Main PCB
  • Display Interface Board
  • Wiring Harness

Related codes

Full explanation for E088
E090

Your boiler has detected a problem with the sensor that monitors exhaust gases, and it has shut down as a safety precaution.

High Engineer only £120-£220

Parts commonly replaced

  • Exhaust NTC probe
  • Wiring harness
  • Main PCB

Related codes

Full explanation for E090
E091

Your boiler has detected that dirt or debris is building up inside the main heating unit, which is preventing it from transferring heat effectively.

High Engineer only £150-450

Parts commonly replaced

  • Primary heat exchanger
  • Heat exchanger gaskets
  • Central heating filter

Related codes

Full explanation for E091
E092

Your boiler has failed its internal self-checking process and has shut down as a safety precaution.

High Engineer only £120-350

Parts commonly replaced

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

Related codes

Full explanation for E092
E093

Your boiler has tried and failed to automatically adjust its gas settings too many times and has now locked itself out for safety.

High Engineer only £120-350

Parts commonly replaced

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

Related codes

Full explanation for E093
E094

Your boiler has detected an issue with how the gas and air are mixing, prompting the system to shut down for safety.

High Engineer only £140-350

Parts commonly replaced

  • Lambda sensor
  • Gas valve
  • Electronic control board

Related codes

Full explanation for E094
E095

Your boiler has failed its internal self-check to ensure it is burning gas efficiently and safely.

High Engineer only £100-350

Parts commonly replaced

  • Ionisation Electrode
  • Gas Valve
  • PCB

Related codes

Full explanation for E095
Showing 41–48 of 48
E096

Your boiler has detected an issue with the air and gas mixture used for combustion and has shut down for safety.

High Engineer only £180-450

Parts commonly replaced

  • Lambda Sensor
  • Gas Valve
  • Electrode Set
  • PCB

Related codes

Full explanation for E096
E097

Your boiler has failed an internal safety check during startup and has stopped running for your protection.

High Engineer only £180-350

Parts commonly replaced

  • Main Printed Circuit Board (PCB)
  • Wiring harness

Related codes

Full explanation for E097
E098

Your boiler's automatic gas control system has failed to calibrate properly, meaning it cannot safely regulate the fuel it needs to stay alight.

High Engineer only £180-450

Parts commonly replaced

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

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 the boiler power off at the fused spur switch (the wall switch).
  2. Wait for at least 30 seconds.
  3. Turn the power back on to clear the software lockout.

Parts commonly replaced

  • No parts usually required
  • Printed Circuit Board (PCB)

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 and needs to be topped up.

High DIY-safe £0-120

What to check first

  1. Locate the filling loop (the flexible silver hose) underneath or near your boiler.
  2. Slowly open the small valve handles until you hear water entering the system.
  3. Watch the pressure gauge and close the valves tightly once the needle reaches 1.5 bar.

Parts commonly replaced

  • External Filling Loop
  • Pressure Sensor
  • Expansion Vessel

Related codes

Full explanation for FIL
FWER

Your boiler's internal computer parts are having trouble communicating because their software versions do not match.

High Engineer only £180-350

Parts commonly replaced

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

Related codes

Full explanation for FWER
OBCD

Your boiler's internal computer system has detected a failure with its built-in clock, which may prevent your heating schedules from working correctly.

Medium DIY-safe £180-350

What to check first

  1. Turn the boiler power switch off at the wall socket
  2. Wait for 60 seconds
  3. Turn the power back on to see if the internal clock resets itself

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Control Interface

Related codes

Full explanation for OBCD
SFS

Your boiler is not broken, it is simply reminding you that a routine service is due to ensure everything is running safely and efficiently.

Low Engineer only £80-£120

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 is requesting its scheduled annual service or a routine maintenance check to ensure it continues to run safely and efficiently.
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