This is the most common real-world cause. If the seals on the servo motor or the feedback connector degrade, cutting fluid (coolant), moisture, or oil can penetrate the pulse coder housing. Liquid contamination shorts out the MCU pins, leading directly to the 366 error. 3. Electrical Noise and Interference (EMI)
After addressing the underlying cause, follow these steps to reset and recover from the alarm: fanuc 366 alarm