Water heater does not ignite, burner does not light, display shows E01 shortly after a hot water demand.

Safety first: Turn off electrical power to the heater and close the gas isolation valve before removing covers. If you ever smell gas, do not attempt repair—ventilate the area and contact a gas-safe technician immediately.

Step-by-step checks:

• Verify gas supply: Ensure the external gas isolation valve to the Baxi water heater is fully open. Check that other gas appliances in the home work. If none work, contact your gas supplier.
• Reset the appliance: Restore power, then press the reset button (or follow the reset procedure in the Baxi manual). If E01 returns, continue.
• Inspect ignition electrode and lead: With power and gas off, remove the front cover. Locate the ignition electrode assembly near the burner. Check for cracked porcelain, loose connections, or carbon buildup. Clean the tip gently with fine emery cloth and ensure the lead is firmly connected to the ignition transformer on the Baxi control board.
• Check flame sensor (ionisation probe): Often combined with the ignition electrode on Baxi units. Clean the probe with fine abrasive pad to remove oxidation. Ensure it is correctly positioned in the burner flame path.
• Gas valve and wiring: Confirm the gas valve connector is fully seated on the Baxi gas valve. Look for damaged wiring or signs of overheating. Do not attempt to open or adjust the gas valve yourself.

When to call a professional: If E01 persists after confirming gas supply and cleaning the ignition/flame sensor, a Gas Safe / licensed technician must test gas pressure, ignition voltage, and replace the gas valve or ignition components as needed.