Boiler will not ignite; display shows E01 shortly after a call for heat or domestic hot water

Safety first: Turn off power to the boiler at the service switch and close the gas shutoff valve before removing any covers. If you ever smell gas, do not attempt repair—evacuate and call your gas supplier or emergency services.

• Check gas supply: Verify that the manual gas shutoff valve to the NTI boiler is fully open. Confirm other gas appliances in the home work. If not, contact the gas utility.
• Reset the boiler: Restore power, then press and hold the reset button (or follow the NTI control panel reset procedure) once. Do not repeatedly reset if E01 returns immediately.
• Inspect ignition/flame rod: With power and gas off, remove the front panel, locate the ignition electrode/flame rod assembly at the burner. Check for cracked porcelain, heavy soot, or corrosion. Clean gently with fine emery cloth and re‑seat the wiring connector firmly.
• Check wiring to gas valve: Inspect the harness from the control board to the gas valve for loose plugs, damaged insulation, or burn marks. Reseat connectors.
• Professional checks: A licensed technician should verify inlet gas pressure, manifold pressure, and combustion, and test the gas valve coil resistance. Replace the gas valve or ignition electrode assembly if out of spec.