Boiler locks out with code 01, burner does not ignite, red lockout LED on, fan may start briefly then stop.

Safety first: Switch the boiler off at the main switch and isolate the gas supply before removing the cover. Only a qualified gas engineer should work on gas components and sealed combustion chambers.

• Reset the boiler: Press the reset button as per the Immergas manual. If the fault reappears, continue diagnosis.
• Check gas supply: Ensure other gas appliances work. Verify the gas isolation valve under the boiler is fully open. If no gas supply, contact your gas provider.
• Inspect ignition electrode: With power and gas isolated, remove the front cover. Locate the ignition electrode on the burner. Check for cracks in the ceramic, carbon build-up, or loose wiring. Clean the tip gently with fine emery cloth and re‑seat the electrode ensuring correct position and gap as per Immergas specifications.
• Check ionisation (flame) electrode: Inspect the ionisation probe for contamination or damage. Clean gently and ensure the cable connection to the PCB is firm.
• Check gas valve operation (engineer only): A qualified technician should verify that the gas valve receives power during ignition and that inlet and outlet pressures match Immergas data plate values. Replace the gas valve if it does not open or modulate correctly.
• Final test: Reassemble the boiler, restore gas and power, and run a heating or hot water demand to confirm stable ignition and no further 01 lockouts.