Fanuc 414 Servo Alarm Z Axis Detect Error May 2026

Electrical noise / improper grounding.
If a high-current device (spindle drive, coolant pump) is dumping noise onto the ground line, the servo drive’s position detection circuit can misinterpret feedback.
Fix: Check that motor feedback cable shield is grounded at only the control end, not both ends.

Place a mechanical jack, a 4x4 wooden post, or an industrial spring lift under the spindle head. Then release the Z-axis brake manually (refer to your machine manual) to settle the head on the support. Do not rely on the brake alone. fanuc 414 servo alarm z axis detect error

Alarm 414 = “Servo Alarm: Z-axis – Detect Error.”
This means the CNC control unit commanded the Z-axis motor to move, but the Position Coder (pulse coder) or the servo system failed to return a valid feedback signal within the expected parameters. It’s essentially a “loss of control” alarm. Electrical noise / improper grounding

Troubleshooting a Z-axis detection error requires extreme caution. Because the system has lost track of the position, the machine may not know where the floor or the work table is located. | Diagnostic No

Alarm 414 occurs
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Can you manually move Z-axis (handwheel)? 
    ├─ NO → Brake likely stuck OR mechanical lock
    │        → Check brake relay / voltage
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Jog Z-axis while watching DGN 204
    ├─ 204 = 0 → No feedback → Replace encoder cable or pulse coder
    ├─ 204 moves but jerky → Mechanical binding or motor magnet loss
    ├─ 204 matches command but error large → Increase parameter 1828 temporarily (test only)
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Swap servo drive with another axis
    ├─ Fault moves to X or Y → Replace drive
    ├─ Fault stays on Z → Motor or cable problem

Diagnosis: The control sees a voltage imbalance or feedback mismatch at standstill. This is rarely mechanical.

While this alarm can happen on X, Y, or Z, it’s most common on the Z-axis because: