Boiler starts then shuts down with E02, fan runs briefly but burner does not stay lit.

Safety: Isolate electrical power before removing the boiler case. Gas and combustion checks must be done by a Gas Safe engineer.

User checks:

• Press the reset button once and observe if the boiler lights and runs normally.
• Ensure the flue terminal is not obstructed by debris, snow, or vegetation.

Engineer checks:

• Remove and inspect the flame sensor (ionisation probe) on the EHC burner assembly; clean light deposits with fine abrasive pad and refit, ensuring correct gap and position.
• Check the burner and combustion chamber for heavy soot or corrosion; clean or replace burner if necessary.
• Verify all earth connections between burner, chassis and PCB are secure and free of corrosion.
• Measure ionisation current during operation and compare with EHC specifications; if low, suspect sensor, wiring or PCB.
• Check gas valve settings and combustion with a flue gas analyser; adjust within manufacturer’s limits.

Persistent E02 faults after cleaning and wiring checks usually indicate a failing flame sensor or main PCB that should be replaced.