401
Drive Ready Signal (DRDY) Lost
Fanuc · αi series AC Servo Motor
What does 401 mean?
The DRDY (Drive Ready) signal has transitioned to 0, indicating that the servo amplifier is not in a ready state. This often occurs during initial power-up or after a fault, preventing motor operation.
Common Causes
- Servo amplifier internal readiness conditions not met.
- Initial power-up sequence not completed or interrupted.
Repair Steps
- 1
Cycle power to the servo amplifier.
- 2
Verify power supply stability and input voltage levels for the servo amplifier.
Verified technical data. Last updated: March 2026
Source: Fanuc αi series AC Servo Motor