Firebird Enviro System Fault codes & diagnostics

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

System Oil 12-44 kW 2010-present

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.
13 High
Just want the most common Firebird Enviro System faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 13 documented codes

Tap any card for details

BURNER LOCKOUT

Your boiler has shut down because it cannot safely ignite or maintain its flame, often due to a fuel supply issue or a dirty component.

High DIY-safe £120-300

What to check first

  1. Check that your external oil tank has plenty of fuel.
  2. Ensure all oil supply valves between the tank and the boiler are fully open.
  3. Press the illuminated reset button on the burner once (if it fails again, do not continue trying and call a technician).

Parts commonly replaced

  • Oil nozzle
  • Photocell
  • Flexible oil hose
  • Fuel pump
Full explanation for BURNER LOCKOUT
Burner Lockout A

Your boiler has stopped working because it cannot get enough oil to keep the flame going.

High DIY-safe £90-180

What to check first

  1. Check the oil level in your storage tank to ensure you haven't run out.
  2. Inspect the oil supply line valve to make sure it is fully open.
  3. Press the illuminated reset button on the burner once; do not press it more than twice.

Parts commonly replaced

  • Oil filter
  • Photocell
  • Oil pump
  • Nozzle

Related codes

Full explanation for Burner Lockout A
Burner Lockout B

Your boiler has stopped working because it has detected an issue with its electricity supply or internal wiring.

High DIY-safe £90-250

What to check first

  1. Check if other electrical appliances in your home are working to rule out a power cut.
  2. Ensure your boiler's power switch or fused spur is turned on.
  3. Press the manual reset button on the burner control box once to see if the system restarts.

Parts commonly replaced

  • Burner Control Box
  • Internal Wiring Harness
  • Capacitor
Full explanation for Burner Lockout B
Burner Lockout C

Your boiler's burner has shut itself down for safety because it failed to light or stay lit properly.

High DIY-safe £120-350

What to check first

  1. Check that you have enough oil in your storage tank.
  2. Ensure the oil supply valves are fully open.
  3. Press the illuminated manual reset button on the burner once only.

Parts commonly replaced

  • Photocell
  • Oil nozzle
  • Ignition transformer
  • Oil pump
Full explanation for Burner Lockout C
Burner Lockout D

Your boiler's burner has stopped working for safety reasons, meaning the system cannot fire up to provide heating or hot water.

High DIY-safe £120-350

What to check first

  1. Check that you have enough heating oil in your storage tank.
  2. Ensure the oil supply valves are fully open.
  3. Press the illuminated reset button on the burner once; if it fails to restart or locks out again immediately, do not keep pressing it.

Parts commonly replaced

  • Oil nozzle
  • Photocell
  • Control box
  • Fuel pump
Full explanation for Burner Lockout D
Burner Lockout E

Your boiler's burner has stopped working because it cannot spray fuel properly to create a flame.

High Engineer only £120-190

Parts commonly replaced

  • Oil nozzle
  • Oil filter
  • Flexible oil hose
Full explanation for Burner Lockout E
Burner Lockout F

Your boiler has shut down because it has detected an issue with how the exhaust gases are being cleared through the flue system.

High Engineer only £120-350

Parts commonly replaced

  • Flue pipe seals
  • External flue terminal
  • Condensate trap

Related codes

Full explanation for Burner Lockout F
E1

Your boiler's internal temperature sensor has stopped sending a reliable signal, which means the system cannot safely regulate heat.

High Engineer only £120-220

Parts commonly replaced

  • NTC thermistor
  • Wiring harness

Related codes

Full explanation for E1
E2

Your boiler has detected a problem with the sensor that monitors exhaust gas temperatures, causing the system to shut down for safety.

High Engineer only £120-220

Parts commonly replaced

  • Flue thermistor
  • Connecting wiring harness

Related codes

Full explanation for E2
E3

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

High Engineer only £120-190

Parts commonly replaced

  • Flue Thermistor
  • Wiring Harness
  • Main PCB

Related codes

Full explanation for E3
E5

Your boiler's burner has stopped working for safety reasons, meaning the system cannot fire up to provide heat or hot water.

High DIY-safe £90-250

What to check first

  1. Check that you have enough heating oil in your storage tank.
  2. Ensure the oil supply valves are fully open.
  3. Press the reset button on the burner control box once; if it fails again, do not keep resetting it and call an engineer.

Parts commonly replaced

  • Photocell
  • Oil nozzle
  • Fuel pump
  • Control box

Related codes

Full explanation for E5
High limit

Your boiler has reached an unsafe temperature and has automatically shut down to prevent damage or dangerous overheating.

High DIY-safe £120-350

What to check first

  1. Check that all radiator valves are open and not turned off.
  2. Ensure there is enough water pressure in the system by checking the pressure gauge.
  3. Press the manual reset button located on the control panel or behind the front cover.

Parts commonly replaced

  • Circulation pump
  • High limit thermostat
  • System filter (cleaning/replacement)
Full explanation for High limit
SAFETY HIGH LIMIT THERMOSTAT

Your boiler has switched itself off because it got too hot, acting as a safety measure to prevent damage.

High DIY-safe £90-180

What to check first

  1. Wait for the boiler to cool down completely (at least 20-30 minutes).
  2. Locate the manual reset button for the high limit thermostat, usually found under a black screw cap on the control panel.
  3. Unscrew the cap and firmly press the small reset button inside.
  4. Restart the boiler and check that your radiator valves are open and the pump is running.

Parts commonly replaced

  • Overheat Thermostat
  • Circulating Pump
  • Control Thermostat
Full explanation for SAFETY HIGH LIMIT THERMOSTAT