Toshiba S11 Fault Codes List

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Troubleshoot your Toshiba VF-S11 drive with our updated fault code guide. Learn to interpret OC, OL, and OP trips, access the trip history, and reset faults safely.

Toshiba S11 Fault Codes Reference Table

Below is the complete list of trip codes and alarms. Please refer to this table to match the flashing code on your inverter with the specific hardware or parameter issue.

Toshiba S11 Fault Codes List

Toshiba S11 Fault Codes List

Fault Code and Meaning Cause and Remedy
OC1 / OC1P
(0001 / 0025)

Overcurrent during acceleration		 Cause:
  • The acceleration time (ACC) is too short.
  • The V/F setting is improper.
  • A restart signal is input to the rotating motor after a momentary stop.
  • A special motor (e.g. motor with small impedance) is used.

Remedy:
  • Increase the acceleration time (ACC).
  • Check the V/F parameter.
  • Use F301 (auto-restart) and F302 (ride-through control).
  • Adjust the carrier frequency (F300).
  • Set the carrier frequency control mode selection parameter F316 to 1 or 3.
OC2 / OC2P
(0002 / 0026)

Overcurrent during deceleration		 Cause:
  • The deceleration time (dEC) is too short.

Remedy:
  • Increase the deceleration time (dEC).
  • Set the carrier frequency control mode selection parameter F316 to 1 or 3.
OC3 / OC3P
(0003 / 0027)

Overcurrent during constant speed operation		 Cause:
  • The load fluctuates abruptly.
  • The load is in an abnormal condition.

Remedy:
  • Reduce the load fluctuation.
  • Check the load (operated machine).
  • Set the carrier frequency control mode selection parameter F316 to 1 or 3.
OC1P / OC2P / OC3P
(0025 / 0026 / 0027)

Ground fault trip / Arm overcurrent at start-up		 Cause:
  • A current leaked from an output cable or the motor to ground.
  • A main circuit element is defective.

Remedy:
  • Check cables, connectors, and so on for ground faults.
  • Make a service call.
OCL
(0004)

Overcurrent (load side at start-up)		 Cause:
  • The insulation of the output main circuit or motor is defective.
  • The motor has too small impedance.
  • A 11 or 15 kW model was started, although a current is leaked from an output cable or the motor to ground.

Remedy:
  • Check the cables and wires for defective insulation.
  • When using a 11 or 15 kW model, check cables and connectors for ground faults.
OCR
(0005)

Arm overcurrent at start-up		 Cause:
  • A main circuit element is defective.

Remedy:
  • Make a service call.
EPH1
(0008)

Input phase failure		 Cause:
  • A phase failure occurred in the input line of the main circuit.
  • The capacitor in the main circuit lacks capacitance.

Remedy:
  • Check the main circuit input line for phase failure.
  • Enable F608 (input phase failure detection).
  • Check the capacitor in the main circuit for exhaustion.
EPH0
(0009)

Output phase failure		 Cause:
  • A phase failure occurred in the output line of the main circuit.

Remedy:
  • Check the main circuit output line, motor, etc. for phase failure.
  • Enable F605 (Output phase failure detection).
OP1
(000A)

Overvoltage during acceleration		 Cause:
  • The input voltage fluctuates abnormally.
  • A restart signal is input to the rotating motor after a momentary stop.

Remedy:
  • Insert a suitable input reactor.
  • Use F301 (auto-restart) and F302 (ride-through control).
OP2
(000B)

Overvoltage during deceleration		 Cause:
  • The deceleration time (dEC) is too short.
  • F304 (dynamic braking resistor) is off.
  • F305 (overvoltage limit operation) is off.
  • The input voltage fluctuates abnormally.

Remedy:
  • Increase the deceleration time (dEC).
  • Install a dynamic braking resistor.
  • Enable F304 and F305.
  • Insert a suitable input reactor.
OP3
(000C)

Overvoltage during constant-speed operation		 Cause:
  • The input voltage fluctuates abnormally.
  • The motor is in a regenerative state because the load causes the motor to run at a frequency higher than the inverter.

Remedy:
  • Insert a suitable input reactor.
  • Install a dynamic braking resistor.
OL1
(000D)

Inverter overload		 Cause:
  • The acceleration time (ACC) is too short.
  • The DC braking amount is too large.
  • The V/F setting is improper.
  • The load is too large.

Remedy:
  • Increase the acceleration time.
  • Reduce DC braking amount (F251) and time (F252).
  • Check V/F parameter setting.
  • Use an inverter with a larger rating.
OL2
(000E)

Motor overload		 Cause:
  • The V/F setting is improper.
  • The motor is locked up.
  • Low-speed operation is performed continuously.
  • An excessive load is applied to the motor.

Remedy:
  • Check the V/F parameter setting.
  • Check the load (operated machine).
  • Adjust OLM to the overload the motor can withstand.
OLr
(000F)

Dynamic braking resistor overload trip		 Cause:
  • The deceleration time is too short.
  • Dynamic braking is too large.

Remedy:
  • Increase the deceleration time (dEC).
  • Increase the capacity of dynamic braking resistor and adjust PBR capacity parameter F308.
Ot
(0020)

Over-torque trip		 Cause:
  • Over-torque reaches a detection level during operation.

Remedy:
  • Enable F615 (over-torque trip selection).
  • Check system error.
OH
(0010)

Overheat		 Cause:
  • The cooling fan does not rotate.
  • The ambient temperature is too high.
  • The vent is blocked up.
  • A heat generating device is installed close to the inverter.
  • The thermistor in the unit is broken.

Remedy:
  • Restart after cooling down.
  • Replace fan if not rotating.
  • Secure sufficient space around the inverter.
  • Make a service call.
OH2
(002E)

External thermal trip		 Cause:
  • An external thermal trip is input.

Remedy:
  • Check the external thermal input.
E
(0011)

Emergency stop		 Cause:
  • During automatic/remote operation, a stop command is entered from the operation panel.

Remedy:
  • Reset the inverter.
EEP1
(0012)

EEPROM fault 1		 Cause:
  • A data writing error occurs.

Remedy:
  • Turn off the inverter, then turn it again. If error persists, make a service call.
EEP2
(0013)

EEPROM fault 2		 Cause:
  • Power supply is cut off during tyP operation and data writing is aborted.

Remedy:
  • Turn power off temporarily and turn back on, then try tyP operation again.
EEP3
(0014)

EEPROM fault 3		 Cause:
  • A data reading error occurred.

Remedy:
  • Turn off the inverter, then turn it again. If error persists, make a service call.
Err2
(0015)

Main unit RAM fault		 Cause:
  • The control RAM is defective.

Remedy:
  • Make a service call.
Err3
(0016)

Main unit ROM fault		 Cause:
  • The control ROM is defective.

Remedy:
  • Make a service call.
Err4
(0017)

CPU fault 1		 Cause:
  • The control CPU is defective.

Remedy:
  • Make a service call.
Err5
(0018)

Remote control error		 Cause:
  • An error arises during remote operation.

Remedy:
  • Check the remote control device, cables, etc.
Err7
(001A)

Current detector fault		 Cause:
  • The current detector is defective.

Remedy:
  • Make a service call.
Err8
(001B)

Optional circuit board format error		 Cause:
  • An optional circuit board in a different format is installed.

Remedy:
  • Check circuit board connection and reset power.
  • Replace the circuit board with a correctly formatted one.
UC
(001D)

Low-current operation Trip		 Cause:
  • The output current decreased to a low-current detection level.

Remedy:
  • Enable F610 (low-current detection).
  • Check detection level setting (F611, F612).
UP1
(001E)

Undervoltage trip (main circuit)		 Cause:
  • The input voltage (in the main circuit) is too low.

Remedy:
  • Check the input voltage.
  • Enable F627 (undervoltage trip selection).
  • Enable F302 and F301 for momentary stops.
EF2
(0022)

Ground fault trip		 Cause:
  • A ground fault occurs in the output cable or the motor.

Remedy:
  • Check the cable and the motor for ground faults.
Etn1
(0054)

Auto-tuning error		 Cause:
  • Check motor parameter F401 to F494.
  • Motor capacity is 2 classes or less than the inverter.
  • Output cable is too thin.
  • Motor is rotating.

Remedy:
  • Check connections and motor parameters.
EtyP
(0029)

Inverter type error		 Cause:
  • Circuit board is changed.

Remedy:
  • Make a service call.
E-18
(0032)

Break in analog signal cable		 Cause:
  • The signal input via VIA is below the analog signal detection level set with F633.

Remedy:
  • Check cables for breaks. Check F633 setting.
E-19
(0033)

CPU communications error		 Cause:
  • A communications error occurs between control CPUs.

Remedy:
  • Make a service call.
E-20
(0034)

Excessive torque boosted		 Cause:
  • The torque boost parameter F402 is set too high.
  • The motor has too small impedance.

Remedy:
  • Decrease the setting of F402.
E-21
(0035)

CPU fault 2		 Cause:
  • The control CPU is defective.

Remedy:
  • Make a service call.
SOUt
(002F)

Step-out (For PM motor only)		 Cause:
  • The motor shaft is locked.
  • One output phase is open.
  • An impact load is applied.

Remedy:
  • Unlock the motor shaft.
  • Check interconnect cables.
OFF

ST terminal OFF		 Cause:
  • The ST-CC circuit is opened.

Remedy:
  • Close the ST-CC circuit.
MOFF

Undervoltage in main circuit		 Cause:
  • The supply voltage between R, S and T is under voltage.

Remedy:
  • Measure the main circuit supply voltage.
rtry

Retry in process		 Cause:
  • The inverter is in the process of retry.
  • A momentary stop occurred.

Remedy:
  • The inverter is normal if it restarts automatically.
Err1

Frequency point setting error alarm		 Cause:
  • The frequency setting signals at points 1 and 2 are set too close to each other.

Remedy:
  • Set the frequency setting signals at points 1 and 2 apart from each other.
CLr

Clear command acceptable		 Cause:
  • This message is displayed when pressing the STOP key while an error code is displayed.

Remedy:
  • Press the STOP key again to clear the trip.
EOFF

Emergency stop command acceptable		 Cause:
  • The operation panel is used to stop operation in automatic or remote control mode.

Remedy:
  • Press the STOP key for an emergency stop. Press any other key to cancel.
HI / LO

Setting error alarm		 Cause:
  • An error is found in a setting when data is reading or writing.

Remedy:
  • Check whether the setting is made correctly.
db

DC braking		 Cause:
  • DC braking in process.

Remedy:
  • The message goes off in several tens of seconds if no problem occurs.
dbon

Shaft fixing control		 Cause:
  • Motor shaft fixing control is in process.

Remedy:
  • Normal if message disappears when stop command is entered.
E1 / E2 / E3

Flowing out of excess number of digits		 Cause:
  • The number of digits such as frequencies is more than 4.

Remedy:
  • Lower the frequency free unit magnification F702.
StOP

Momentary power failure slowdown stop		 Cause:
  • The slowdown stop prohibition function set with F302 is activated.

Remedy:
  • To restart operation, reset the inverter or input an operation signal again.
LStP

Auto-stop (continuous low-limit frequency)		 Cause:
  • The automatic stop function selected with F256 was activated.

Remedy:
  • Deactivate the automatic stop function or increase frequency command.
Init

Parameters in the process of initialization		 Cause:
  • Parameters are being initialized to default values.

Remedy:
  • Normal if the message disappears after a while.
E-17

Operation panel key fault		 Cause:
  • The RUN or STOP key is held down for more than 20 seconds.
  • The RUN or STOP key is faulty.

Remedy:
  • Check the operation panel.
Atn1

Auto-tuning		 Cause:
  • Auto-tuning in process.

Remedy:
  • Normal if the message disappears after a few seconds.
 

How to Read S11 Faults via LED Keypad

The S11 features a simple but effective interface. In 2026, diagnosing this drive relies on navigating the “Monitor” menu using the potentiometer dial:

  • Current Fault: When the drive trips, the display alternates between the fault code (e.g., OC1) and the operational data. Note the code immediately.
  • Trip History: The S11 stores the last 4 faults. Press the MON (Monitor) key repeatedly until you see the trip history parameter (often displayed as nErr or within the AUH menu). Rotate the dial to scroll through Past Trip 1 through 4.
  • Status Monitoring: You can view the output current (`C***`) and voltage (`P***`) in real-time. If the current reading fluctuates wildly before a trip, you likely have a mechanical load issue.

General Troubleshooting Steps

Because S11 drives are aging, check for both parameter errors and physical wear:

  1. Overcurrent (OC1/OC2/OC3): OC1 is Accel, OC2 is Decel, OC3 is Constant Speed. This is the most common fault. Check for a short circuit in the motor wiring or a locked rotor. If the fault occurs instantly upon start with no motor connected, the drive’s internal transistors are likely blown.
  2. Overload (OL1/OL2): OL1 is Motor Overload; OL2 is Inverter Overload. Ensure the “Motor Rated Current” (Parameter tHr) is set correctly. If the motor is running at low speeds (under 30Hz) without a cooling fan, it may overheat and trigger OL1.
  3. Overvoltage (OP1/OP2/OP3): High DC bus voltage. This often happens during deceleration. Increase the Deceleration Time (Parameter dEC) or check if the braking resistor (if equipped) is connected properly.

Frequently Asked Questions (FAQ)

Q: What does the flashing “C” or “P” code mean?

A: These are Alarms, not faults. A flashing C indicates the drive is in Current Limit (slowing down to avoid an OC trip). A flashing P indicates DC Bus Voltage ripple is high, often due to a lost input phase. The drive continues to run during these alarms.

Q: How do I reset a Toshiba S11 fault?

A: You can reset the drive using one of these methods:

  • Press the STOP/RESET key on the keypad twice.
  • Momentarily close the RES (Reset) terminal to the Common (CC) terminal.
  • Cycle the main input power (Turn OFF, wait for the display to go dark, Turn ON).

Q: Why does the drive display “OFF”?

A: OFF indicates the drive is powered up, healthy, and in Standby mode. It is simply waiting for a Run command via the terminal strip or the keypad.

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