Firebird Enviro 15-20 Fault codes & diagnostics

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

Regular Oil 15-20 kW

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Note it down before pressing reset — resetting clears the code immediately. How to read fault codes →

Just want the most common Firebird Enviro 15-20 faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 4 documented codes

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E1

Your boiler's internal temperature sensor has stopped communicating correctly with the main control board, preventing the system from heating up.

High Engineer only £120-190

Parts commonly replaced

  • NTC Control Thermistor
  • Wiring Harness

Related codes

Full explanation for E1
E2

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 £120-210

Parts commonly replaced

  • Flue Thermistor (NTC Sensor)
  • Connecting Wiring Harness

Related codes

Full explanation for E2
E3

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 £120-210

Parts commonly replaced

  • Flue gas thermistor
  • Wiring harness connectors
  • Main PCB

Related codes

Full explanation for E3
E5

Your boiler's burner has stopped working correctly and has entered a safety lockout mode to prevent damage.

High DIY-safe £120-350

What to check first

  1. Check that you have sufficient oil in your storage tank.
  2. Ensure the oil supply valve on the tank is fully open.
  3. Press the illuminated reset button on the front of the burner once.

Parts commonly replaced

  • Photocell
  • Oil pump
  • Control box
  • Nozzle

Related codes

Full explanation for E5