Yaskawa V1000 Alarm & Fault Codes: Troubleshooting Guide
What the Fault Code Means
The V1000 keypad displays the exact alarm or fault text listed in the OEM V1000 Technical Manual, including codes such as oC, ov, Uv1, oH, oL1, oL2, GF, LF, PF, EF, and the CPF series. An alarm indicates an abnormal condition while the drive may keep running; a fault stops drive output immediately and holds the motor at zero output until the cause is corrected and the fault is reset. When a fault trips, the code latches on the display, the output transistors are disabled, and the connected motor coasts or stops depending on the load and any mechanical brake. The full fault index, including Uv2, Uv3, LF2, CF, bb, and option-card faults, is documented in the manual for the specific voltage class and software revision installed on that unit.
Common Causes and Related Codes
Most V1000 faults trace back to a small set of root causes, and the most likely should be checked first. oC (overcurrent) is usually caused by too-short acceleration time, a jammed or overloaded machine, incorrect motor wiring, an output short, or a ground fault. ov (overvoltage) most often comes from excessive regenerative energy, too-short deceleration, an overhauling load, high incoming voltage, or a bad braking resistor or braking circuit. Uv1 (undervoltage) typically points to low or interrupted input power, phase loss, voltage sag on starting, loose connections, or a failed rectifier or precharge circuit. oH and oH1 usually mean blocked airflow, a failed fan, a dirty heatsink, high ambient temperature, or sustained overload. oL1 and oL2 point to mechanical overload, incorrect motor parameter data, or a drive selected too small for the load. GF and LF point to insulation failure or an open output phase; PF points to lost or unbalanced input power.
- oL1/oL2 – overload on the motor or drive, often paired with high current readings.
- GF/LF – ground fault or open output phase, usually a wiring or motor insulation problem.
- PF/Uv1 – input-side power problems, from blown fuses to phase loss.
- CPF codes – control or processor faults on the drive’s own boards.
Step by Step Troubleshooting
Follow a consistent sequence rather than resetting repeatedly:
- Record the exact code, subcode, and fault history before touching anything.
- Lock out and tag out incoming power per site procedure before opening the enclosure or touching terminals.
- Allow the DC bus to discharge per the manual before working inside the drive.
- Inspect input and output wiring, terminals, and connectors for looseness, heat damage, or shorts.
- Measure input voltage on all three phases under load, and check output current balance.
- Check the driven machine for binding, jams, or excess load if the fault correlates with acceleration or running current.
- Verify motor insulation resistance with the motor disconnected, using a suitable test procedure.
- Confirm cooling fan operation, heatsink cleanliness, and enclosure airflow for thermal-related codes.
- Compare drive and motor nameplate data against the configured parameters.
Clearing and Resetting the Fault
Do not use the reset key as a substitute for finding the cause; repeated resets on overcurrent, ground fault, overload, overtemperature, undervoltage, or overvoltage events can damage power semiconductors and connected equipment. Once the initiating condition is corrected and confirmed safe, issue the configured fault reset or press the operator RESET key. For an oL1 fault specifically, the V1000 manual requires the U4-16 monitor value to be below 100 before the fault can be reset, so verify this reading before attempting to clear the code. Cycle input power only if the manual permits it for that fault and the code does not clear with a keypad reset. After reset, confirm the motor restarts safely, recheck relevant parameters against nameplate and application data, and run the machine under load to confirm the original condition does not return before returning it to production.
When It Is a Hardware Failure
Some faults point to a failing component rather than an application or wiring issue. Repeated oC with the motor disconnected points to the inverter power module, current-sensing circuit, gate-drive circuit, or control board rather than the load, and should be confirmed with isolation testing and semiconductor checks before parts are replaced. LF that persists with the motor leads disconnected indicates the drive’s output section itself needs repair or replacement, not the motor or cable. Uv1 that persists after verifying clean input power can indicate a failed rectifier, precharge circuit, DC-link capacitor, or voltage-detection circuit. GF that reappears after the motor and cable test good on insulation points back to a failed inverter power module. A recurring CPF code generally means a control-board fault rather than a nuisance trip, and typically requires control-board or drive repair rather than repeated power cycling.
How Robotics Integration Helps
Robotics Integration works with maintenance teams on V1000, J1000, and A1000 drives that are down or faulting intermittently. Over the phone, technicians walk through the displayed code, fault history, and wiring checks to separate an application or wiring problem from a drive failure before parts are pulled. When a component-level repair is needed, the shop tests and repairs power modules, gate-drive circuits, current sensors, DC-bus capacitors, precharge circuits, control boards, and connectors, and evaluates fans and rectifiers as part of the same repair. On-site service is available for wiring verification, load testing, and startup after a repair or replacement, including running the drive under representative load to confirm the original fault condition does not return. Because V1000, J1000, and A1000 code strings can look similar but carry different thresholds and parameters, work is done against the specific manual for the model, voltage class, and software revision installed.
Looking up a different code? See the full FANUC and robot alarm code list, or read about our Yaskawa drive repair.
What to Send and How to Reach Us
Before calling, have the following ready: the drive model and voltage class (V1000, J1000, or A1000), the exact alarm or fault text as displayed including any subcode, the fault history stored in the drive, the axis or motor involved, and a description of what the machine was doing when the fault occurred, such as accelerating, running steady, decelerating, or sitting at rest. Note any recent changes to load, wiring, incoming power, or environment, and have photos of the keypad display and drive nameplate on hand if possible, since these details speed up diagnosis. Call 1-602-449-1556 to talk through the fault with a technician, arrange component repair, or schedule on-site troubleshooting for a drive that is down or faulting repeatedly.
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