Controller display shows E01 and the Aquabion softener does not start a regeneration cycle.

Safety first: Turn off electrical power to the softener at the breaker or unplug the power supply. Close the inlet and outlet isolation valves and relieve pressure by opening a nearby tap.

• Check for obvious blockages: Close the inlet valve to the Aquabion unit. Remove the inlet union and inspect the inlet venturi and turbine flow sensor for debris, scale, or sand. Rinse under running water and gently spin the turbine wheel to ensure it moves freely.
• Inspect wiring: Remove the controller cover. Locate the flow sensor harness (usually a 2–3 wire plug near the inlet). Ensure the connector is fully seated on both the sensor and the main control board. Look for pinched, cut, or corroded wires and repair or replace as needed.
• Test the sensor: With power restored briefly, enter the diagnostic mode (refer to Aquabion service manual for your model) and monitor the flow reading while slowly opening the inlet valve. If the display still shows zero flow while water is clearly moving, the turbine flow sensor is likely defective.
• Replace components if needed: If cleaning and reseating connections do not clear E01, replace the turbine flow sensor assembly. If a new sensor does not restore operation, the main control board may be faulty and should be replaced by a qualified technician.

Warning: Do not operate the unit with covers removed and power applied unless you are trained and understand electrical safety. Always depressurize the plumbing before removing any wet components.