Toshiba H9 Fault Codes List

Troubleshoot your Toshiba H9 HVAC drive with our updated fault code guide. Learn to interpret OC, OL, and EPH trips, view the LCD trip history, and reset faults.

Toshiba H9 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 LCD display with the specific hardware or parameter issue.

H9 ASD Faults, Alarms, and Notification Codes

Fault Code and Meaning	Cause and Remedy
Atn Autotune active	Cause: Atn indicates that the Autotune function is active. Remedy: Notification only; usually momentary under normal conditions. Wait for function to complete.
dbOn DC Braking	Cause: This code conveys the DC Injection function being carried out. Remedy: Display shows db when braking. Display shows dbOn when the motor shaft stationary function is being carried out.
CM1 Comm1 Error	Cause: Internal communications error. Remedy: Improperly programmed ASD. Improper communications settings. Improperly connected cables.
CM2 Comm2 Error	Cause: External communications error. Remedy: Improperly programmed ASD. Improper communications settings. Improperly connected cables.
E Emergency Off	Cause: Output signal from the ASD is terminated and a brake may be applied if so configured. Remedy: Stop|Reset pressed twice at the EOI. EOFF command received remotely. ASD reset required.
MOFF Main Under-Voltage	Cause: Under-voltage condition at the 3-phase AC input to the ASD. Remedy: Low 3-phase commercial voltage.
OC Over-Current	Cause: ASD output current greater than F601 setting. Remedy: Defective IGBT (U, V, or W). ASD output to the motor is connected incorrectly. ASD output phase-to-phase short. The ASD is starting into a spinning motor. Motor/machine jammed. Mechanical brake engaged while the ASD is starting or while running. Accel/Decel time is too short. Voltage Boost setting is too high. Load fluctuations. ASD operating at an elevated temperature.
OH Overheat	Cause: ASD ambient temperature excessive. Remedy: 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.
OJ Timer	Cause: Run-time counter exceeded. Remedy: Type Reset required; select Clear run timer.
OLI ASD Overload	Cause: Load requirement in excess of the capability of the ASD. Remedy: The carrier frequency is too high. An excessive load. Acceleration time is too short. DC damping rate is set too high. The motor is starting into a spinning load after a momentary power failure. The ASD is improperly matched to the application.
OLM Motor Overload	Cause: Load requirement in excess of the capability of the motor. Remedy: V/f parameter improperly set. Motor is locked. Continuous operation at low speed. The load is in excess of what the motor can deliver.
OLR Resistor Overload	Cause: Excessive current at the Dynamic Braking Resistor. Remedy: Deceleration time is too short. DBR configuration improperly set.
OP Over-Voltage	Cause: DC bus voltage exceeds specifications. Remedy: ASD attempting to start into a spinning motor after a momentary power loss. Incoming commercial power is above the specified range. Decel time is too short. Voltage spikes at the 3-phase input; install inductive filter. DBR required. DBR resistance value is too high. DBR function is turned off. Over-Voltage Stall feature is turned off. System is regenerating. Load instability. Disable the Ridethrough function (F302).
OT Over-Torque	Cause: Torque requirement is in excess of the setting of F616 or F617 for a time longer than the setting of F618. Remedy: ASD is not correctly matched to the application. F616 or F617 setting is too low. Obstructed load.
POFF Control Under-Voltage	Cause: Under-voltage condition at the 5, 15, or the 24 VDC supply. Remedy: Defective Control board. Excessive load on power supply. Low input voltage.
PtSt Reference Point	Cause: Two speed-reference frequency setpoint values are too close to each other. Remedy: Two speed reference frequency setpoints are too close to each other (increase the difference).
UC Under-Current	Cause: Output current of the ASD is below the level defined at F611 and remains there for a time longer than the setting of F612. Remedy: Output current too low.
E-10 Sink/Source Setting Error	Cause: Sink/Source configuration is incorrect. Remedy: Improperly positioned Sink/Source jumper on the Terminal board or on an option device (see J100). Check Sink/Source configuration.
E-11 Brake Sequence Response Error	Cause: Braking sequence error. Remedy: F630 is set to a non-zero value. Braking sequence discrete input and output terminals are not setup properly.
E-12 Encoder Signal-Loss Error	Cause: ASD is configured to receive a signal from a shaft-mounted encoder and no signal is being received while running. Remedy: Disconnection at the Encoder circuit. Motor is stopped and is generating torque via torque limit control. ASD is not configured properly.
E-13 Speed Error	Cause: Result of a motor speed that is greater than the commanded speed when using an encoder for speed control. Remedy: Improper encoder connection or setup information. Defective encoder.
E-17 Key Failure	Cause: Key failure detected. Remedy: Same key input for 20 seconds or more.
E-18 Analog (Terminal) Input Loss	Cause: V/I signal loss. Remedy: Terminal Board failure. P24 over-current condition. F633 setting is too high.
E-19 CPU Communication Error	Cause: CPU data Transmit/Receive error. Remedy: Check CPU communications.
E-20 V/f Control Error	Cause: Torque processing error. Remedy: Make service call.
E-21 CPU Processing Error	Cause: Software processed incorrectly. Remedy: Make service call.
E-22 Logic Input Voltage Error	Cause: Incorrect voltage applied to the discrete input terminals. Remedy: Check input terminal voltages.
E-23 Optional Expansion Input Terminal Board 1 Error	Cause: Optional Expansion Input Terminal Board 1 is defective. Remedy: Replace board.
E-24 Optional Expansion Input Terminal Board 2 Error	Cause: Optional Expansion Input Terminal Board 2 is defective. Remedy: Replace board.
E-25 Stop Positioning Retention Error	Cause: Load movement while stopped. Remedy: F381 setting is too low. Encoder malfunction. Creep speed is too high.
E-26 CPU2 Fault	Cause: CPU malfunction. Remedy: Control board malfunction.
E-50 / E-51 Sink/Source Setting Error	Cause: Sink/Source configuration is incorrect. Remedy: Improperly positioned Sink/Source jumper on the Terminal board or on an option device (see J100).
EEP1 EEPROM Fault	Cause: EEPROM write malfunction. Remedy: Make a service call.
EEP2 / EEP3 EEPROM Read Error	Cause: EEPROM read malfunction. Remedy: Make a service call.
EF1 / EF2 (Earth) Ground Fault	Cause: Ground fault at output. Remedy: Ground fault at the motor. Ground fault at the output of the ASD. Current leakage to Earth Ground.
EPHI Input Phase Failure	Cause: 3-phase input to the ASD is low or missing at the R, S, or T input terminals. Remedy: Check input power wiring.
EPHO Output Phase Failure	Cause: 3-phase output from the ASD is low or missing at the U, V, or W output terminals or at the input to the motor. Remedy: Check output wiring and motor.
ERR2 RAM Fault	Cause: Internal RAM malfunction. Remedy: Make a service call.
ERR3 ROM Fault	Cause: Internal ROM malfunction. Remedy: Make a service call.
ERR4 CPU Fault	Cause: CPU malfunction. Remedy: Control board malfunction. Make a service call.
ERR5 Communication Error	Cause: Communication time out error or malfunction. Remedy: Improper or loose connection. Improper system settings.
ERR6 Gate Array Fault	Cause: Main Gate Array is defective. Remedy: Make a service call.
ERR7 Low-Current	Cause: Improper Low-Current detection level settings. Remedy: Check settings at F609 – F612.
ERR8 Option Device Fault	Cause: Option device error. Remedy: Check installation, connections, and option device manual.
ERR9 Flash Memory Fault	Cause: Flash memory malfunction. Remedy: Make a service call.
ETN Autotune Error	Cause: Autotune readings that are significantly inconsistent with the configuration information. Remedy: A non-3-phase motor is being used. Incorrect settings at F400 or F413. Using a motor that has a significantly smaller rating than the ASD. ASD output cabling is too small, too long, or is being housed in a cable tray with other cables that are producing an interfering EMF. Motor is running during the Autotune function.
ETN1 Autotune Error 1	Cause: Autotune adjustment required. Remedy: F402 adjustment required (Motor temperature is too high). F410 adjustment required (Motor Constant 1 improperly set).
ETN2 Autotune Error 2	Cause: Autotune adjustment required. Remedy: F412 adjustment required (Motor Constant 3 improperly set).
ETN3 Autotune Error 3	Cause: Problem with Motor Constant readings. Remedy: Autotune setting F400 is set to Auto Calculation.
ETYP Typeform Error	Cause: Firmware information (typeform) loaded into the Gate Driver board is inconsistent with the device. Remedy: The Gate Driver board has been replaced. The Gate Driver board is defective.
None No Errors	Cause: No active faults. Remedy: System Normal.
OC1 Over-Current During Acceleration	Cause: Over-Current condition during startup/acceleration. Remedy: Improper V/f setting. Restart from a momentary power outage. The ASD is starting into a rotating motor. ASD/Motor not properly matched. Phase-to-phase short (U, V, or W). Accel time too short. Voltage Boost setting is too high. Motor/machine jammed. Mechanical brake engaged while the ASD is running. ASD current exceeds 340% of the rated FLA (or 320% for >100HP).
OC1P Overheat During Acceleration	Cause: Overheating detected during acceleration. Remedy: Cooling fan inoperative. Ventilation openings are obstructed. Internal thermistor is disconnected. Acceleration time is too short. Improper V/f setting. ASD or the motor is improperly matched to the application.
OC2 Over-Current During Deceleration	Cause: Over-Current condition during deceleration. Remedy: Phase-to-phase short (U, V, or W). Deceleration time is too short. Motor/machine jammed. Mechanical brake engaged while the ASD is running. ASD current exceeds thresholds (340% or 320%).
OC2P Overheat During Deceleration	Cause: Overheating detected during deceleration. Remedy: Cooling fan inoperative. Ventilation openings are obstructed. Internal thermistor is disconnected. Deceleration time is too short. DC Injection current is too high. ASD or the motor is improperly matched to the application.
OC3 Over-Current During Run	Cause: Over-Current condition during constant speed run. Remedy: Load fluctuations. ASD is operating at an elevated temperature. ASD current exceeds thresholds (340% or 320%).
OC3P Overheat During Run	Cause: Overheating detected during run. Remedy: Cooling fan inoperative. Ventilation openings are obstructed. Internal thermistor is disconnected. Improper V/f setting. ASD or the motor is improperly matched to the application.
OCA1 / OCL U-Phase Over-Current	Cause: Low impedance at the U lead of the ASD output. Remedy: Check output cabling and motor.
OCA2 / OCL V-Phase Over-Current	Cause: Low impedance at the V lead of the ASD output. Remedy: Check output cabling and motor.
OCA3 / OCL W-Phase Over-Current	Cause: Low impedance at the W lead of the ASD output. Remedy: Check output cabling and motor.
OCR Dynamic Braking Resistor Over-Current	Cause: ASD inability to discharge the bus voltage during regeneration. Remedy: No dynamic braking resistor (DBR) installed. Deceleration time is too short. Improper DBR setup information. Defective IGBT7 (or IGBT7 ckt.). 3-phase input voltage is above specification.
OH2 External Overheat	Cause: Excessive-heat signature received at the TB3 terminals. Remedy: Check TH1(+) and TH1(-) terminals. See F637 for setup information.
OL1 ASD Overload	Cause: ASD Overload detected. Remedy: Acceleration time is too short. DC Injection current is too high. Improper V/f setting. Motor running during restart. ASD or the motor is improperly matched to the application.
OL2 Motor Overload	Cause: Motor Overload detected. Remedy: Improper V/f setting. Motor is locked. Continuous operation at low speed. Load requirement exceeds ability of the motor. Startup frequency setting adjustment required.
OLR Dynamic Braking Resistor Overload	Cause: Resistor Overload detected. Remedy: Deceleration time is too short. DBR setting adjustment required. Over-Voltage Stall setting adjustment required.
OP1 Over-Voltage During Acceleration	Cause: Motor running during restart. Remedy: Check restart conditions.
OP2 Over-Voltage During Deceleration	Cause: Over-Voltage detected during deceleration. Remedy: Deceleration time is too short. DBR value is too high. DBR required (DBR setup required). Stall protection is disabled. 3-phase input voltage is out of specification. Input reactance required.
OP3 Over-Voltage During Run	Cause: Over-Voltage detected during run. Remedy: Load fluctuations. 3-Phase input voltage out of specification. DBR required (DBR setup required).
OT Over-Torque	Cause: Torque requirement by the load is in excess of the setting of F616 or F617 for a time longer than the setting of F618. Remedy: The ASD is improperly matched to the application. The load is obstructed.
SOUT Step-Out (for PM Motor Only)	Cause: Step-Out condition detected. Remedy: Motor shaft is locked. Output phase is open. Operating a reciprocating load.
UP1 Main Power Under-Voltage	Cause: Input 3-phase voltage is too low. Remedy: Momentary power failure longer than the time setting of F628.
UP2 Control Power Under-Voltage	Cause: Under-voltage condition at the 5, 15, or the 24 VDC supply. Remedy: 3-phase input voltage low.

 

How to Read H9 Faults via LCD Keypad (EOI)

The H9’s Electronic Operator Interface (EOI) is designed for facility managers and HVAC technicians. In 2026, you can access deep diagnostic data directly from the wall-mounted keypad without needing a laptop:

• Trip History: The H9 records the last 4 faults. Press the MON (Monitor) button and scroll down to “Trip History.” This will show you the chronological order of failures.
• Status at Trip: By selecting a specific past trip and pressing ENT (Enter), you can view the “At-Trip” data. This includes the output frequency, current, and voltage at the exact moment the drive tripped—crucial for diagnosing if a pump was ramping up or running steady.
• Terminal Status: You can view the status of the input terminals (RES, S1, S2, etc.) to see if an external safety interlock, such as a “Fireman’s Override” or “Freeze Stat,” triggered the shutdown.

General Troubleshooting Steps

Before resetting an HVAC drive, ensure you check the mechanical systems:

1. Overcurrent (OC1/OC2/OC3): Short circuit or ground fault. For HVAC, check for water intrusion in the motor conduit or a locked rotor on a pump. Perform a megger test if the fault persists.
2. Overload (OL1/OL2): OL1 is Motor Overload; OL2 is Drive Overload. Check for slipping belts, closed dampers preventing airflow (causing backpressure), or seized bearings on the fan shaft.
3. Input Phase Failure (EPH1): This indicates a loss of one of the incoming power phases. Check your building’s fuses or circuit breakers immediately, as running on single-phase can damage the drive’s input rectifier.

Frequently Asked Questions (FAQ)

Q: What is the difference between a Warning (C code) and a Fault?

A: A Warning (flashing codes starting with “C”, like CM00) alerts you to a condition—such as high current—but allows the fan or pump to keep running. A Fault (codes like OC or E) instantly stops the output to protect the equipment.

Q: How do I reset a Toshiba H9 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 CC (Common).
• Cycle the main power (Turn OFF, wait for the screen to go black, Turn ON).

Q: Why does the drive display “OFF”?

A: OFF means the drive is powered and ready but has no “Run” command. In HVAC, this often means the Building Automation System (BAS) is not calling for the unit to run, or the “Auto/Manual” switch is in the wrong position.