State gas tankless water heater will not ignite; display shows E01 shortly after a hot water tap is opened.

Safety first: Turn the gas control valve to OFF, shut off the manual gas shutoff valve, and disconnect electrical power before removing covers. Allow the heater to cool completely.

• Check gas supply: Verify the manual gas shutoff valve to the State heater is fully open. Confirm other gas appliances in the home work normally. If gas supply is questionable, contact your gas utility or a licensed plumber.
• Inspect the igniter: Remove the front cover per the State service manual. Locate the igniter assembly near the burner. Check for cracks, heavy carbon buildup, or loose wiring. Gently clean the igniter tip with fine emery cloth and ensure the connector is fully seated on the control board.
• Check flame sensor: Many State tankless units use a combined igniter/flame rod. Clean the flame rod with fine steel wool to remove oxidation. Ensure the ceramic insulator is not cracked.
• Burner and orifice: Inspect the main burner and orifices for dust, lint, or spider webs. Use compressed air to blow debris away (do not use sharp tools that can deform orifices).
• Reset and test: Restore power and gas, then open a hot water tap. If E01 persists after cleaning and confirming gas supply, the ignition module or gas valve may require professional diagnosis.