Fanuc 366 Alarm May 2026

To confirm it's NOT a hardware failure:

(Note: The exact wording may vary slightly depending on the FANUC series – 0i, 16i/18i/21i, 31i, etc.) fanuc 366 alarm

If the alarm persists after a power cycle, you need the Fanuc PMC parameter and Ladder III software. To confirm it's NOT a hardware failure:

Official Fanuc Description: “Pulse coder connection disconnection (axis).” (Note: The exact wording may vary slightly depending

What does that actually mean? Your CNC control sends a command to the servo motor to move. The motor spins, and a device called a Pulse Coder (or encoder) attached to the motor shaft measures exactly how far it turned. It sends this data back to the control via a feedback cable.

Alarm 366 triggers when: The control is sending power to the motor to move it, but it is receiving no feedback signal (or an invalid signal) from the Pulse Coder. Essentially, the control is "blind" to the motor's position. Because the control cannot verify where the axis is, it kills the power immediately to prevent a crash.

Note: This alarm typically applies to digital servo motors (such as the Fanuc $\alpha$ series and newer).