Digital U.S. Motors pool pump controller will not start the motor; display shows E01 and beeps once when START is pressed.

Safety first: Turn off power at the pool sub‑panel breaker and verify with a non-contact voltage tester before touching any wiring.

• Check supply voltage: Remove the controller cover and measure line-to-line (for 230V) or line-to-neutral (for 115V) at the pump input terminals with a multimeter. Compare to the nameplate rating on the U.S. Motors pump. If more than ~10% low, the controller may lock out with E01.
• Inspect connections: Tighten line lugs at the pump terminal block and at the breaker. Look for heat discoloration or melted insulation that indicates a loose or high-resistance connection.
• Check wire size and run length: Confirm the wire gauge meets U.S. Motors installation specs for the motor HP and distance. Long runs with undersized wire cause voltage drop; consider upgrading wiring if voltage at the pump is low but normal at the panel.
• Reset the controller: After correcting any wiring or supply issues, turn the breaker OFF for 60 seconds, then ON. Clear the error by pressing STOP/RESET (if provided) and then START.
• If voltage is normal but E01 persists: The internal low-voltage sensing circuit on the drive/control board may be faulty and the controller may need replacement.