Fanuc 414 Servo Alarm Z Axis Detect Error //top\\ Jun 2026
Excessive friction or a "tight" axis brake can cause the motor to draw extra current, leading the amplifier to interpret it as an overload.
In the Fanuc control system, a 414 alarm signifies that the has flagged an issue. While the 414 code tells you "which" axis is failing (Z-axis), the diagnostic bits tell you "why." Check Diagnostic 200 (Z-Axis) Before replacing parts, check the diagnostic screen: Bit 2 (HCAL): High current alarm. Bit 5 (OVC): Overcurrent/Overload. Bit 6 (LV): Low voltage. Bit 7 (OV): Overvoltage. 🛠️ Common Causes and Solutions 1. Faulty Servo Amplifier The Z-axis servo amplifier is the most frequent culprit. fanuc 414 servo alarm z axis detect error
Start: 414 on Z ↓ Power cycle? → Clears? → Intermittent (check battery/cable) ↓ No Check battery → Low? → Replace + reset absolute ↓ OK Inspect Z encoder cable → Damage? → Replace cable ↓ OK Reseat connectors at motor & amp → Clears? → Done ↓ No Swap Z & Y cables at amplifier → 414 moves to Y? → Fix Z cable ↓ No Swap Z & Y amplifiers → 414 moves to Y? → Replace Z amplifier ↓ No Replace Z motor pulse coder (encoder) Excessive friction or a "tight" axis brake can
| Cause | Description | |-------|-------------| | | Broken wire, intermittent connection, or poor shielding on Z-axis encoder cable. | | 2. Encoder internal failure | A20B-2000/2001 series or alpha pulse coder failed (common on older machines). | | 3. Loose connector | JX5, JX6, or JFB connector on servo amp or CNC side. | | 4. Servo amplifier failure | Loss of 5V encoder power supply inside amplifier. | | 5. Noise interference | High-frequency noise from spindle drive, VFD, or poor grounding. | | 6. Battery voltage low | On absolute encoders – low battery can corrupt position data (often shows 310/349 first). | Bit 5 (OVC): Overcurrent/Overload
| Diagnostic No. | Meaning | Normal Range | | :--- | :--- | :--- | | DGN. 200 | Position error (current) | Should track command | | DGN. 203 | Command pulse count | Changes when moving | | DGN. 204 | Feedback pulse count | Must match 203 | | DGN. 205 | Load meter % | < 150% normal |
| If you have... | Then... | | :--- | :--- | | Basic tools and electrical safety knowledge | Perform Steps 1–4 (mechanical + cable + diagnostics) | | A spare servo drive | Swap test first (fastest isolation) | | No spare parts | Check brake voltage and encoder continuity immediately | | An intermittent alarm (comes and goes) | Replace Z-axis encoder cable – 90% success rate |
