Firebird Enviro Combi 26 Fault codes & diagnostics

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

Combi Oil 26 kW 2010-present

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Severity at a glance

Each cell = one fault code. Hover to identify.
7 High 2 Low
Just want the most common Firebird Enviro Combi 26 faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 9 documented codes

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Central Heating Active (Green)

Your boiler is working correctly and is currently providing heat to your radiators as requested by your thermostat.

Low DIY-safe £0

What to check first

  1. No action is required as this indicates normal operation.
  2. If you want the heating to turn off, lower the temperature on your room thermostat.
  3. Check that your heating timer or programmer is set to the 'Off' or 'Timed' position if you did not expect the heating to be on.
Full explanation for Central Heating Active (Green)
E1

Your boiler's internal temperature sensor has stopped communicating correctly, preventing the system from heating up as a safety precaution.

High Engineer only £120-£200

Parts commonly replaced

  • NTC Temperature Thermistor
  • Wiring Harness

Related codes

Full explanation for E1
E2

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

  • Flue thermistor (NTC sensor)
  • Wiring harness connecting to thermistor

Related codes

Full explanation for E2
E3

Your boiler has detected an issue with the sensor that monitors exhaust gas temperatures and has shut down as a safety precaution.

High Engineer only £120-£210

Parts commonly replaced

  • Flue thermistor
  • Connecting wiring harness

Related codes

Full explanation for E3
E5

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

High DIY-safe £120-280

What to check first

  1. Check if you have run out of heating oil in your storage tank.
  2. Ensure the oil supply valve is fully open.
  3. Press the manual reset button on the burner control box once (do not repeat if it fails).

Parts commonly replaced

  • Oil nozzle
  • Photocell
  • Fuel pump
  • Ignition transformer

Related codes

Full explanation for E5
High Limit Thermostat (Yellow)

Your boiler has automatically shut down because the water inside has become far too hot, acting as a safety precaution to prevent damage.

High DIY-safe £90-180

What to check first

  1. Check that all your radiator valves are open and not turned to the off position.
  2. Inspect the system pressure gauge and top up the water if it is below 1 bar.
  3. Wait for the boiler to cool down completely and firmly press the manual reset button located under the control panel cover.

Parts commonly replaced

  • High Limit Thermostat
  • Circulation Pump
  • Flow Temperature Sensor
Full explanation for High Limit Thermostat (Yellow)
Lockout (Red)

Your boiler's burner has stopped working and has gone into a safety shutdown mode to prevent further damage.

High DIY-safe £100-£350

What to check first

  1. Check that your external oil tank has plenty of fuel.
  2. Ensure the oil supply valve is fully open.
  3. Press the illuminated red reset button on the burner once to restart it.

Parts commonly replaced

  • Oil nozzle
  • Photocell
  • Fuel pump
  • Ignition transformer
Full explanation for Lockout (Red)
Overheat Condition

Your boiler has become too hot and has automatically shut itself down as a safety precaution.

High DIY-safe £0-120

What to check first

  1. Allow the boiler to cool down completely for at least 20 minutes.
  2. Locate the manual reset button situated at the rear of the electrical control panel.
  3. Press the button firmly until you hear a click to reset the safety thermostat.
  4. Ensure your radiator valves are open and the system pressure is correct before restarting.

Parts commonly replaced

  • Overheat Limit Thermostat
  • Circulation Pump
  • Thermistor
Full explanation for Overheat Condition