Yaskawa V1000 Fault Codes: The Plain-English Reference
The Yaskawa V1000 compact drive reports faults as short letter codes on its LED operator — oC, oV, Uv1 and family. This searchable table is the plain-English decoder: meaning, usual field cause, and where to start.
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| Code | Name | What it means | What to check first |
|---|---|---|---|
| oC | Overcurrent | Output current exceeded the instantaneous trip level | Short/ground fault in motor or cable; sudden load slam; accel too aggressive — inspect before repeated resets |
| oV | Overvoltage | DC bus voltage exceeded the limit | Regenerative load on decel — extend decel time or add braking; check supply for transients |
| Uv1 | Undervoltage | DC bus voltage fell below the limit | Line sag/brownout or lost phase — check supply and input wiring |
| oH / oH1 | Heatsink Overheat | Drive temperature exceeded the alarm/trip level | Clean heatsink, verify fan, check enclosure cooling and ambient |
| oL1 | Motor Overload | Electronic motor thermal overload tripped | Verify motor rated current setting matches nameplate; find the mechanical overload |
| oL2 | Drive Overload | Drive thermal overload — output above rating too long | Check drive sizing vs the real load and duty cycle |
| oL3 | Overtorque 1 | Output current exceeded the configured overtorque detection level | Investigate the mechanical load — jam, binding, or process change |
| GF | Ground Fault | Ground leakage current detected on the output | Insulation-test the motor and cable; look for moisture ingress |
| SC | Short Circuit / IGBT | Output short-circuit or power-transistor fault detected | Inspect motor and cable for shorts; persistent SC with motor disconnected = drive power stage |
| LF | Output Phase Loss | An output phase to the motor was lost | Check motor lead connections at both ends |
| PF | Input Phase Loss | Excessive DC bus ripple — an input phase is missing/imbalanced | Check incoming three-phase supply, fuses, and terminals |
| EF0-EF8 | External Fault | An external fault input (terminal S1-S8 or comms) is active | The number tells you which terminal — check the device wired to it |
| CE | Comm Error (Modbus) | MEMOBUS/Modbus communication was lost | Check RS-485 wiring, termination, addresses, and the master |
| bUS | Option Comm Error | Communication lost on the option-card network | Check option card seating and network health |
| oPr | Operator Disconnect | The keypad/operator was disconnected while the drive was set to require it | Reseat the operator or change the run-source configuration |
| CoF | Current Offset | Current-detection offset drifted out of range | Cycle power; persistent CoF suggests drive hardware service |
| FbL | PID Feedback Loss | The PID feedback signal fell below the loss-detection level | Check the transmitter and its wiring (classic 4-20 mA break symptom) |
| STo | Safe Torque Off | The safe-disable inputs are open | Check the safety circuit wired to the safe-disable terminals; jumpers per manual if STO is unused |
| Err | EEPROM Write Error | Parameter memory write failed | Retry; persistent Err means control board memory trouble |
Clearing faults on a V1000
Fix the cause, then reset: press RESET/Stop on the operator, toggle a digital input configured for fault reset, reset over Modbus from the controller, or cycle power. The drive stores a fault history in its monitor parameters — read it before clearing; a pattern across the history (five Uv1 events overnight, say) is a diagnosis in itself.
Reading Yaskawa's code language
- o-prefix = "over" — oC overcurrent, oV overvoltage, oH overheat, oL overload. The suffix number points at motor (1) vs drive (2) vs detection functions (3+).
- Uv = undervoltage, with Uv1 the main bus-undervoltage trip.
- EF + number = external fault by terminal — the drive is relaying a message from whatever you wired to that input; the drive itself is fine.
- Two-letter hardware codes (GF, SC, LF, PF) — the electrical-integrity family: when these appear, the cable and motor deserve the megger before the reset button.
Drive fundamentals live in our VFD guide; the Allen-Bradley equivalent table is at PowerFlex 525 fault codes.
Frequently asked questions
What does oC mean on a Yaskawa V1000?
Overcurrent: the output current spiked past the instantaneous trip level. Usual suspects are a short or ground fault in the motor cable or motor, a mechanical slam load, or too-aggressive acceleration — inspect before resetting repeatedly.
What does Uv1 mean on a Yaskawa drive?
Main-circuit undervoltage: the DC bus dropped below its limit, almost always from supply sag, a brownout, or a lost input phase. Check incoming power and connections.
How do I reset a fault on a V1000?
Remove the cause, then press RESET on the operator, toggle a reset-configured digital input, reset via Modbus, or cycle power. Check the fault history in the monitor parameters first — patterns are diagnoses.
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