Toshiba Q9+ Plus Fault Codes List

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Troubleshoot your Toshiba Q9+ Plus HVAC drive with our updated fault code guide. Learn to interpret OC, OL, and EPH trips, view the EOI trip history, and reset faults.

Toshiba Q9+ Plus Fault Codes Reference Table

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

Toshiba Q9+ Plus Fault Codes List

Toshiba Q9+ Plus Fault Codes List

Fault Code and Meaning Cause and Remedy
Atn
Autotune Active		 Cause:
  • Autotune function is active.

Remedy:
  • Information only; wait for completion.
nErr
No Error		 Cause:
  • No active errors.

Remedy:
  • None required.
LOFr
Virtual Linear Pump Low Frequency		 Cause:
  • Virtual Linear Pump function is operating at the Low-Frequency Limit setting.

Remedy:
  • Information only.
Pump
Virtual Linear Pump On		 Cause:
  • Virtual Linear Pump function is enabled and active.

Remedy:
  • Information only.
4-20 mA
4-20 Signal Loss		 Cause:
  • Misconnection, poor connection, or broken wire.
  • Improper programming at F201 and associated parameters.

Remedy:
  • Check wiring and connections.
  • Verify parameter F201 settings.
*OL1
ASD Overload		 Cause:
  • Carrier frequency is too high.
  • Excessive load.
  • Acceleration time is too short.
  • DC damping rate is too high.
  • Motor is starting into a spinning load after a momentary power failure.
  • ASD is improperly matched to the application.

Remedy:
  • Reduce carrier frequency or load.
  • Increase acceleration time.
  • Check DC damping settings.
CM1
Comm Error Interruption		 Cause:
  • Improperly programmed ASD.
  • Improper communications settings.

Remedy:
  • Verify ASD programming and communication settings.
CM2
Comm Error 2		 Cause:
  • Improperly connected cables.

Remedy:
  • Check communication cables and connections.
DAMP
Damper Closed		 Cause:
  • Improper configuration/programming for Damper Control at discrete input terminals.

Remedy:
  • Check Damper Control configuration.
*OP
DC Bus Over-Volts		 Cause:
  • ASD is attempting to start into a spinning motor after a momentary power loss.
  • Incoming commercial power voltage level is above the specified range.
  • Deceleration time is too short.
  • Voltage spikes at the 3-phase input.
  • Over-Voltage Stall feature is turned off.
  • System is regenerating / Load fluctuations.

Remedy:
  • Install inductive filter if spikes are present.
  • Increase deceleration time.
  • Enable Over-Voltage Stall feature.
*POFF
DC Under-Volts		 Cause:
  • Defective control board.
  • Excessive load on power supply.
  • Low input voltage.

Remedy:
  • Check input voltage.
  • Check for excessive load.
E
Emergency Off		 Cause:
  • Stop-Reset was pressed twice at the EOI.
  • E-OFF command was received remotely.

Remedy:
  • Reset the system.
HLd
Heavy Load		 Cause:
  • Acceleration time is too short.
  • ASD is improperly matched to the application.
  • Excessive load.

Remedy:
  • Increase acceleration time.
  • Verify drive sizing for the load.
LLd
Light Load		 Cause:
  • ASD is improperly matched to the application.

Remedy:
  • Verify drive sizing.
LLt
Lower Limit Time		 Cause:
  • Lower-Limit Time reached.

Remedy:
  • Parameter F256 adjustment is required.
MOFF
Main Under-Volts		 Cause:
  • 3-phase input voltage low.
  • Defective control board.
  • Excessive load on power supply.

Remedy:
  • Under-Voltage/Ridethrough settings require adjustment.
OLM
Motor Overload		 Cause:
  • V/f setting requires adjustment.
  • Motor is locked.
  • Continuous operation at low speed.
  • Motor is improperly matched to the load.

Remedy:
  • Adjust V/f settings.
  • Check for mechanical binding/locking.
OC
Over-Current		 Cause:
  • Phase-to-phase short (U/T1, V/T2, or W/T3).
  • Defective IGBT.
  • ASD output to the motor is connected incorrectly.
  • ASD is attempting to start into a spinning motor.
  • Motor/machine is jammed.
  • Mechanical brake engaged while ASD is running.
  • Acceleration/deceleration time is too short.
  • Voltage Boost setting is too high.
  • V/f setting adjustment is required.

Remedy:
  • Check motor and cabling for shorts.
  • Adjust Acceleration/Deceleration times.
  • Check mechanical brakes and load.
*OH
Over-Heating		 Cause:
  • ASD is operating at an elevated temperature.
  • ASD is too close to heat-generating equipment.
  • Cooling fan vent is obstructed.
  • Cooling fan is inoperative.
  • Internal thermistor is disconnected.

Remedy:
  • Check cooling fans and vents.
  • Ensure proper ambient temperature and clearance.
Ot
Over-Torque		 Cause:
  • ASD is improperly matched to the application.
  • Parameter F616 or F617 setting is too low.
  • Obstructed load.

Remedy:
  • Adjust parameters F616 or F617.
  • Check for load obstructions.
LtA
Part Replace		 Cause:
  • Part Replacement Alarm at F634 timed out.

Remedy:
  • Perform required maintenance and reset timer.
OJ
Run-Time Counter		 Cause:
  • User-Set Run-Time Counter Exceeded.

Remedy:
  • Type Reset is required; select Clear run timer.
OLSt
Soft Stall		 Cause:
  • Overload Soft Stall Active.

Remedy:
  • Soft Stall selection adjustment is required (F017).
PtC
Thermal Err		 Cause:
  • Option Thermal Sensor Threshold Exceeded.

Remedy:
  • User-set thermal threshold setting of F646 is exceeded.
UC
Under-Current		 Cause:
  • Output Current of the ASD is Below the Level Defined at F611.

Remedy:
  • Disable detection at F610.
  • Parameter F611 adjustment is required.
E-19
Abnormal CPU2		 Cause:
  • Abnormal CPU2 Communication.

Remedy:
  • Service call is required.
E-18
Analog Input Loss		 Cause:
  • V/I input terminal configured for operation but the voltage/current input is either missing or low.
  • Over-current at P24.

Remedy:
  • Check analog input signals and P24 connection.
E-10
Analog Input OV		 Cause:
  • Analog Input Terminal Over-Voltage.

Remedy:
  • Mis-wire at the ASD input terminals; check wiring.
OL1
ASD Overload (Trip)		 Cause:
  • Acceleration time is too short.
  • DC Injection current is too high.
  • V/f setting needs to be adjusted.
  • Motor is running during restart.
  • ASD/motor is improperly matched to the application.

Remedy:
  • Adjust acceleration time or DC Injection settings.
  • Adjust V/f settings.
Err2
ASD RAM Fault		 Cause:
  • ASD RAM Fault.

Remedy:
  • Service call is required.
Err3
ASD ROM Fault		 Cause:
  • ASD ROM Fault.

Remedy:
  • Service call is required.
EtyP
ASD Type Error		 Cause:
  • Firmware information (typeform) loaded into the Application Board is inconsistent with the Motor Control Board.
  • Application Board or Motor Control Board is defective.

Remedy:
  • Service call is required.
E-26
CPU Fault		 Cause:
  • CPU Fault.

Remedy:
  • Service call is required.
EEP2, EEP3
Ctrl Read Err		 Cause:
  • Initial Read Error (Parameter Initialization).

Remedy:
  • Service call is required.
Err7
Current Err		 Cause:
  • Current Detection Hardware Error.
  • Improper low-current detection level setting.
  • Motor (phase) is disconnected.

Remedy:
  • Check motor connections.
  • Check detection level settings.
E-22
Discrete In Volts		 Cause:
  • Discrete input terminal configured for operation and the input activation voltage level is out of specification.

Remedy:
  • Check input voltage levels.
EEP1
EEPROM Write Err		 Cause:
  • EEPROM Fault (Writing Error).

Remedy:
  • Service call is required.
Etn
Autotuning Err		 Cause:
  • Autotune readings are inconsistent with the configuration.
  • Non-3-phase motor is being used.
  • Improper settings at F400 or F410 – F413.
  • Using a motor with significantly smaller rating than ASD.
  • ASD output cabling is too small/long or has EMF interference.
  • Motor is running during Autotune.

Remedy:
  • Verify motor type and ratings.
  • Check parameters F400-F413.
Etn2
Leak Inductance Err		 Cause:
  • Autotuning Error — Leak Inductance Error.

Remedy:
  • Improper setting at F412; adjust setting.
Etn3
Motor Rating Err		 Cause:
  • Autotuning Error — Motor Rating Error.

Remedy:
  • Improper setting at F405, F406, or F407; adjust settings.
Etn1
Torque Boost Err		 Cause:
  • Autotuning Error — Torque Boost Error.

Remedy:
  • Improper setting at F410; adjust setting.
E
Emergency Off (Trip)		 Cause:
  • Stop-Reset was pressed twice at the EOI.
  • E-Off command was received remotely.

Remedy:
  • Select stopped method at F603.
E-12
Encoder Loss		 Cause:
  • Encoder signal is not received.

Remedy:
  • Check encoder connections.
Err6
Gate Array Fault		 Cause:
  • Defective gate array or gate array malfunction.

Remedy:
  • Service call is required.
EF1, EF2
Ground Fault		 Cause:
  • Mis-wired ground.
  • Loose ground connection.

Remedy:
  • Check ground wiring and connections.
EPH1
Input Phase Failure		 Cause:
  • Mis-wired input phase.
  • Loose input phase connection.

Remedy:
  • Check input phase wiring.
UC
Low-Current (Trip)		 Cause:
  • Improper low-current detection level setting.

Remedy:
  • Adjust detection level setting.
Err8
Net Card Err		 Cause:
  • Optional device malfunction.
  • Improper system settings (at ASD or optional device).
  • Loose or improper connection.

Remedy:
  • Check network option card settings and connections.
OH2
Option Over-Heat		 Cause:
  • Over temperature condition detected by option board.

Remedy:
  • Check PTC1 or PTC2 (see F637 and F638).
EPH0
Output Phase Failure		 Cause:
  • Mis-wired output phase.
  • Loose output phase connection.

Remedy:
  • Check output wiring.
OCL
Output Short		 Cause:
  • ASD is starting into a rotating motor.
  • Phase-to-phase short (U/T1, V/T2, or W/T3).
  • Acceleration time is too short.
  • Motor/machine is jammed or brake engaged.

Remedy:
  • Short Circuit Detection adjustment is required (F613).
  • Check motor and mechanical systems.
OC1, OC1P
Over-Current Acc		 Cause:
  • V/f setting needs to be adjusted.
  • Restart from a momentary power outage.
  • Phase-to-phase short.
  • Acceleration time is too short.

Remedy:
  • Adjust V/f or acceleration settings.
  • Check for shorts.
OC2, OC2P
Over-Current Dec		 Cause:
  • Deceleration time is too short.
  • Motor/machine is jammed or brake engaged.

Remedy:
  • Increase deceleration time.
  • Check mechanical system.
OC3, OC3P
Over-Current Run		 Cause:
  • ASD/Motor is improperly matched to the application.
  • Load fluctuations.
  • ASD is operating at an elevated temperature.

Remedy:
  • Check load and drive sizing.
  • Check environmental conditions.
E-13
Over-Speed		 Cause:
  • Motor speed greater than commanded speed.
  • Improper encoder connection or setup.
  • Defective encoder.

Remedy:
  • Check encoder and speed control settings.
Ot
Over-Torque (Trip)		 Cause:
  • Output torque requirement in excess of F616 or F617 settings for longer than F618 setting.

Remedy:
  • Adjust torque limit settings.
OP1
Over-Voltage Acc		 Cause:
  • Motor is running during restart.

Remedy:
  • Stop motor before restart or use catch-spin.
OP2
Over-Voltage Dec		 Cause:
  • Deceleration time is too short.
  • Stall prevention is disabled.
  • Input reactance is required.

Remedy:
  • Increase deceleration time.
  • Enable stall prevention.
OP3
Over-Voltage Run		 Cause:
  • Load fluctuations.
  • 3-phase input voltage out of specification.

Remedy:
  • Check input voltage stability and load.
E-21
Stack Err		 Cause:
  • Stack Overflow Error.

Remedy:
  • Service call is required.
SOut
Step-Out (PM)		 Cause:
  • Step-Out (For PM Motors Only).

Remedy:
  • Service call is required.
OCA1
U-Phase OC		 Cause:
  • U-Phase Over-Current (Low impedance at U/T1 phase).

Remedy:
  • Check motor winding/cabling for short.
OCA2
V-Phase OC		 Cause:
  • V-Phase Over-Current (Low impedance at V/T2 phase).

Remedy:
  • Check motor winding/cabling for short.
OCA3
W-Phase OC		 Cause:
  • W-Phase Over-Current (Low impedance at W/T3 phase).

Remedy:
  • Check motor winding/cabling for short.
 

How to Read Q9+ Plus Faults via EOI Keypad

The Q9+ Plus EOI is designed to give facility engineers immediate access to crash data without the need for a laptop. In 2026, utilizing the “Monitor” menu is the standard for troubleshooting:

  • Trip History: The Q9+ stores the last 4 major faults. Press the MON (Monitor) button and scroll to “Trip History.” The drive retains these even after a power cycle.
  • At-Trip Data: This is the most critical feature for HVAC. By entering a specific past trip record, you can see the Output Current, Voltage, and Frequency at the exact moment of failure. This helps identify if a pump jammed during startup or if a fan failed at full speed.
  • Cumulative Run Timer: The Q9+ tracks total run time and fan on-time. Use this to determine if a capacitor replacement or fan maintenance is due, potentially preventing future E-19 (CPU/Hardware) faults.

General Troubleshooting Steps

Before resetting the drive, ensure the mechanical side of the HVAC system is clear:

  1. Overcurrent (OC1/OC2/OC3): Short circuit or locked rotor. Check for water in the motor disconnect (common in cooling towers) or a seized pump seal. Perform a megger test on the motor leads.
  2. Overload (OL1/OL2): OL1 is Motor Overload; OL2 is Drive Overload. Check for closed fire dampers causing backpressure on fans, or debris clogging the pump impeller.
  3. Input Phase Failure (EPH1): The Q9+ is sensitive to power quality. Check for blown fuses or a loose connection at the line reactor/disconnect switch.

Frequently Asked Questions (FAQ)

Q: What is the difference between “OL1” and “OL2”?

A: OL1 is the Motor Overload trip, calculated based on the motor’s full load amps (FLA) setting. OL2 is the Inverter Overload trip, meaning the drive itself is overheating or supplying more current than its internal transistors can handle.

Q: How do I reset a Toshiba Q9+ Plus fault?

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

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

Q: Why is the “Fireman’s Override” not working?

A: If the drive is in a fault state (e.g., OC1), it typically will not restart even in Override mode unless the fault is cleared. However, some protection parameters can be disabled in the “Override” menu to force operation during emergencies.

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