AutomationDirect GS Drive Fault Codes

ocA: Over-current during acceleration (ocA); GS4-KPD text: OC at Accel

What it means: Output current went above about 3 times the drive rating (300%) while the motor was speeding up. The drive shuts off its output at once and the motor coasts.^{[1][2][3][4][5][6]}

Likely causes

• Acceleration time too short for the load
• Short circuit or ground fault in the motor cable or motor
• Motor insulation breaking down
• Drive too small for the motor or the load
• Output contactor opening or closing while the drive is putting out voltage
• Torque compensation or V/F voltage set too high

First checks, in this order

1. Disconnect the motor cable from the drive and megger the cable and motor. Replace a cable or motor with poor insulation.
2. Lengthen the acceleration time (GS10/GS20: P01.12; GS4: P1.01) or add S-curve.
3. GS10/GS20: try auto acceleration/deceleration (P01.44) and over-current stall prevention (P06.03).
4. Check that the motor nameplate current is not above the drive rated current.
5. Make sure any output contactor does not switch while the drive is running.
6. GS10/GS20: lower torque compensation gain P07.26 if the motor draws too much current at start.
7. If it trips with the motor disconnected, meter between B1 or DC- and U, V, W for a short and call AutomationDirect Technical Support if you find one.

ocA: Over-current during accel (ocA); GS3 LCD text: OVER-CURRENT ACC

What it means: Current spiked while the drive was ramping up. The manuals list a short at the motor output, torque boost set too high, an acceleration time that is too short, or a drive that is too small.^{[7][8][10][11][13][14]}

Likely causes

• Short circuit at the motor output
• Torque boost too high
• Acceleration time too short
• Drive output capacity too small for the load

First checks, in this order

1. Check the output wiring and motor for poor insulation.
2. Lower the torque boost (GS1/GS2: P2.03; GS3: P2.02).
3. Increase the acceleration time (P1.01 or P1.05).
4. If it keeps tripping, use the next larger drive.

oc: Over-current (oc); GS3 LCD text: OVER-CURRENT

What it means: The drive saw an abnormal rise in output current.^{[7][8][10][11][13][14]}

Likely causes

• Motor horsepower larger than the drive output rating
• Short circuit in the wiring between drive and motor
• Acceleration time too short
• Excessive load on the motor

First checks, in this order

1. Check that the motor horsepower matches the drive output power.
2. Check the drive to motor wiring for short circuits.
3. Increase the acceleration time (P1.01 or P1.05).
4. Check the motor for overload.
5. If the drive still misbehaves after a short is removed, contact AutomationDirect support; the GS1 and GS2 manuals say to send the drive back.

ocd: Over-current during deceleration (ocd); GS4-KPD text: OC at decel

What it means: Output current went above about 3 times the drive rating while the motor was slowing down. Output shuts off at once and the motor coasts.^{[1][2][3][4][5][6]}

Likely causes

• Deceleration time too short
• Motor mechanical brake setting too early
• Short circuit or ground fault at the drive output
• Sudden load change
• Motor cable too long

First checks, in this order

1. Increase the deceleration time (GS10/GS20: P01.13; GS4: P1.02) or the S-curve.
2. Check that a motor brake does not close before the drive has stopped.
3. Megger the motor and motor cable.
4. GS10/GS20: try auto deceleration (P01.44) and over-current stall prevention (P06.03).
5. For a long motor cable, add an output AC reactor or use a larger drive.

ocd: Over-current during decel (ocd); GS3 LCD text: OVER-CURRENT DEC

What it means: Current spiked while the drive was ramping down.^{[7][8][10][11][13][14]}

Likely causes

• Short circuit at the motor output
• Deceleration time too short
• Drive output capacity too small

First checks, in this order

1. Check the output wiring for poor insulation.
2. Increase the deceleration time (P1.02 and P1.06).
3. Use the next larger drive if needed.

ocn: Over-current during steady operation (ocn); GS4-KPD text: OC at Speed

What it means: Output current went above about 3 times the drive rating while running at constant speed. Output shuts off and the motor coasts.^{[1][2][3][4][5][6]}

Likely causes

• Sudden load increase or a jam in the machine
• Locked motor shaft, burnt or aged motor insulation
• Short circuit or ground fault in the motor cable
• Output contactor switching while running
• Motor cable too long

First checks, in this order

1. Look for a jam or shock load on the driven machine.
2. Megger the motor and cable.
3. Check that the motor rated current is not above the drive rating.
4. Make sure no output contactor opens or closes during run.
5. GS10/GS20: lower torque compensation gain P07.26 if it is set high.
6. For a long motor cable, add an output AC reactor or use a larger drive.

ocn: Over-current during steady state (ocn); GS3 LCD text: OVER-CURRENT STD

What it means: Current spiked while the drive was running at set speed.^{[7][8][10][11][13][14]}

Likely causes

• Short circuit at the motor output
• Sudden increase in motor load
• Drive output capacity too small

First checks, in this order

1. Check the output wiring for poor insulation.
2. Check for a stalled motor.
3. Use the next larger drive if needed.

ovd: Over-voltage during deceleration (ovd); GS4-KPD text: OV at Decel

What it means: DC bus voltage went too high while slowing the motor, usually from energy the load pushes back. Trip level: 410 V DC on 120/230 V and 820 V DC on 460 V GS10/GS20 models (1116 V DC on 575 V GS20 models); 450 V DC on 230 V and 900 V DC on 460 V GS4 models.^{[1][2][3][4][5][6]}

Likely causes

• Deceleration time too short for the load inertia
• Braking resistor or braking unit missing or wired wrong
• Supply voltage high or carrying spikes
• Power factor capacitors switching on the same supply
• Ground fault on the motor cable

First checks, in this order

1. Increase the deceleration time (GS10/GS20: P01.13, P01.15, P01.17, P01.19; GS4: P1.02).
2. Fit a braking resistor or braking unit, or check its wiring if one is installed.
3. GS10/GS20: turn on over-voltage stall prevention (P06.01) or auto deceleration (P01.44).
4. Measure the supply voltage and look for spikes; add an AC line reactor if capacitor banks switch on the same supply.
5. Check the motor cable and terminal box for a ground fault.

ovA: Over-voltage during acceleration (ovA); GS4-KPD text: OV at Accel

What it means: DC bus voltage went too high while the motor was speeding up. Trip levels are the same as for ovd.^{[1][2][3][4][5][6]}

Likely causes

• Starting into a motor that is already turning, such as a fan, pump or overhauling load
• Supply voltage high or carrying spikes
• Stall prevention level set below the no-load current (GS10/GS20)
• Ground fault on the motor cable

First checks, in this order

1. Check the supply voltage against the drive rating.
2. GS4: use DC injection at start (P1.25 level, P1.26 time) so a spinning motor stops before the ramp begins.
3. GS10/GS20: use over-voltage stall prevention (P06.01) or auto acceleration (P01.44).
4. If it trips just after acceleration ends, the acceleration time is too short: increase it.
5. Check braking resistor wiring and the motor cable for a ground fault.

ovn: Over-voltage during constant speed (ovn); GS4-KPD text: OV at Speed

What it means: DC bus voltage went too high while running at constant speed.^{[1][2][3][4][5][6]}

Likely causes

• Load driving the motor (regeneration) or sudden load swings
• Supply voltage high or carrying spikes
• Braking resistor or braking unit missing or wired wrong

First checks, in this order

1. Check the input voltage for spikes and check that it is within the drive rating.
2. Add or check a braking resistor or braking unit.
3. GS10/GS20: enable over-voltage stall prevention P06.01.
4. Check the motor cable for a ground fault.

ovS: Over-voltage at stop (ovS); GS4-KPD text: OV at Stop

What it means: GS10/GS20: the DC bus voltage is too high while the drive is stopped. The GS4 manual describes this code as a hardware failure in voltage detection.^{[1][2][3][4][5][6]}

Likely causes

• Supply voltage too high or carrying spikes
• Capacitor banks switching on the same supply
• Internal voltage detection fault

First checks, in this order

1. Measure the supply voltage against the drive rating.
2. Add an AC line reactor if the supply surges.
3. Check braking resistor or braking unit wiring.
4. Cycle power. If cd1, cd2 or cd3 shows afterward, contact AutomationDirect Technical Support.

ov: Over-voltage (ov); GS3 LCD text: OVER-VOLTAGE

What it means: The DC bus voltage went above its maximum allowed value.^{[7][8][9][10][11][12][13][14][15]}

Likely causes

• Input voltage too high or voltage transients
• Motor regeneration during deceleration
• Braking power needed is beyond the drive limits

First checks, in this order

1. Check that the input voltage is within the drive rating.
2. Check for voltage transients on the supply.
3. Increase the deceleration time. GS2 and GS3 can add an optional braking resistor (GS3 20 hp and up needs a dynamic braking unit plus resistor).
4. Check that the braking power needed is within the specified limits.

LvA: Low-voltage during acceleration (LvA); GS4-KPD text: LV at Accel

What it means: The DC bus dropped below the low-voltage level while accelerating. The level is P06.00 on GS10/GS20 (default 180 V DC on 120/230 V, 360 V DC on 460 V, 450 V DC on 575 V models) and P6.35 on GS4.^{[1][2][3][4][5][6]}

Likely causes

• Weak or sagging supply
• Supply too small for the starting load
• Load too heavy or acceleration too fast
• Jumper or DC reactor missing between terminals +1 and +2 (GS10/GS20)

First checks, in this order

1. Measure the input voltage during the start.
2. Check the supply transformer and feeder capacity.
3. Reduce the load or increase the acceleration time.
4. GS10/GS20: check the jumper or DC reactor between +1 and +2.
5. The fault resets once the bus is above P06.00 plus 30 V (GS10/GS20).

Lvd: Low-voltage during deceleration (Lvd); GS4-KPD text: LV at Decel

What it means: The DC bus dropped below the low-voltage level (P06.00 on GS10/GS20, P6.35 on GS4) while decelerating.^{[1][2][3][4][5][6]}

Likely causes

• Supply dip or brownout
• Sudden load change
• Supply capacity too small

First checks, in this order

1. Check the supply voltage and that it matches the drive rating.
2. Check for a sudden load.
3. Increase supply capacity or add a DC reactor.

Lvn: Low-voltage during constant speed (Lvn); GS4-KPD text: LV at Speed

What it means: The DC bus dropped below the low-voltage level (P06.00 on GS10/GS20, P6.35 on GS4) while running at constant speed.^{[1][2][3][4][5][6]}

Likely causes

• Supply dip or brownout
• Sudden load increase
• Supply capacity too small

First checks, in this order

1. Check the supply voltage under load.
2. Reduce the load or use a larger drive if a sudden load causes it.
3. Increase supply capacity or add a DC reactor.

LvS: Low-voltage at stop (LvS); GS4-KPD text: LV at Stop

What it means: The DC bus is below the low-voltage level while the drive is stopped, or a voltage detection problem occurred.^{[1][2][3][4][5][6]}

Likely causes

• Supply off, low or missing a phase
• Supply voltage rating does not match the drive
• Voltage detection hardware fault

First checks, in this order

1. Check the supply voltage and that it matches the drive rating.
2. Fix the supply, then cycle power. If LvS remains, the GS20 manual says to return the drive for repair.
3. Consider a DC reactor or more supply capacity.

Lv: Low voltage (Lv); GS3 LCD text: UNDER-VOLTAGE

What it means: The DC bus voltage fell below its minimum allowed value.^{[7][9][10][12][13][15]}

Likely causes

• Input voltage low or dipping
• Supply problem upstream of the drive

First checks, in this order

1. Check that the input voltage is within the drive rated input voltage.
2. Measure the supply while the drive is running to catch dips.

GFF: Ground fault (GFF); GS4-KPD text: Ground Fault

What it means: The drive detected a short to ground on its output terminals (U, V, W). Output shuts off at once and the motor coasts. The GS4 manual notes the protection is for the drive, not for people.^{[1][2][3][4][5][6]}

Likely causes

• Motor winding insulation breakdown
• Damaged motor cable
• Long motor cable (over 100 m) with high stray capacitance
• Damaged IGBT power module

First checks, in this order

1. Disconnect the motor cable from the drive and megger the motor and cable.
2. Replace a damaged cable.
3. GS10/GS20: with a cable over 100 m, lower the carrier frequency.
4. Keep communication wiring away from power wiring.
5. Cycle power after the checks. If GFF stays, contact AutomationDirect Technical Support.

GFF: Ground fault or fuse failure (GFF); GS3 LCD text: GROUND FAULT

What it means: An output terminal is shorted to ground. The GS2 manual says the short circuit current is over 50% of the drive rating and the power module may be damaged.^{[10][11][12][13][14][15]}

Likely causes

• Poor insulation on the output wiring
• Motor insulation damage
• Damaged IGBT power module
• Unbalanced load or current leakage (GS3)

First checks, in this order

1. Check the motor for insulation damage.
2. Check the output wiring for poor insulation.
3. GS2: check whether the IGBT power module is damaged.

oL: Over load (oL); GS4-KPD text: Overload

What it means: Drive output current stayed above its overload curve too long. On the GS20, variable torque duty allows 120% for 1 minute or 150% for 3 seconds; constant torque duty allows 150% for 1 minute or 200% for 3 seconds.^{[1][2][3][4][5][6]}

Likely causes

• Load too heavy
• Acceleration or deceleration too fast
• V/F mid-point voltage too low, so the motor is weak at low speed
• Long running at low speed with high current
• Broken motor lead or loose terminal screws

First checks, in this order

1. Reduce the load or use a larger drive.
2. GS10/GS20: increase the accel/decel times (P01.12 to P01.19) and check the V/F curve (P01.01 to P01.08).
3. If it only trips at low speed, lower the carrier frequency (P00.17).
4. Check the motor leads for a loose or broken phase.
5. GS4: check whether the motor is overloaded and use the next larger drive if needed.

oL: Overload (oL); GS3 LCD text: OVERLOAD

What it means: The drive output current was too high for too long. The drive can carry 150% of its rated current for up to 60 seconds.^{[7][8][10][11][13][14]}

Likely causes

• Motor overloaded
• Torque compensation set too high
• Drive too small for the application

First checks, in this order

1. Check whether the motor is overloaded.
2. Reduce the torque compensation setting (P2.03).
3. Use a drive with more output capacity.

EoL1: Electronic thermal relay 1 protection (EoL1); GS4-KPD text: Mtr1 Thermal OL

What it means: The drive's thermal model for motor 1 says the motor is overloaded, and the drive coasts to stop. GS10/GS20 start counting above 150% of motor 1 rated current; the trip time is P06.14.^{[1][2][3][4][5][6]}

Likely causes

• Motor overloaded
• Motor rated current or rated frequency entered wrong
• Wrong motor type setting (P06.13)
• Standard motor running at low speed for long periods
• Several motors on one drive

First checks, in this order

1. Check the motor rated current and frequency settings against the nameplate.
2. GS10/GS20: check P06.13 (motor type) and P06.14 (time). For several motors on one drive, set P06.13 = 2 (disable) and fit a thermal relay on each motor.
3. GS4: check the electronic thermal relay setting P6.01.
4. Reduce the load or increase accel/decel times.
5. Check the motor cooling fan.

EoL2: Electronic thermal relay 2 protection (EoL2); GS4-KPD text: Mtr2 Thermal OL

What it means: Same as EoL1, but for motor 2. The drive coasts to stop.^{[1][2][3][4][5][6]}

Likely causes

• Motor 2 overloaded
• Motor 2 rated data entered wrong
• Wrong motor 2 type setting (P06.27)

First checks, in this order

1. Check motor 2 rated current and frequency against the nameplate.
2. GS10/GS20: check P06.27 (motor type) and P06.28 (time), and the motor 2 V/F curve (P01.35 to P01.42).
3. GS4: check the electronic thermal relay setting P6.03.
4. Reduce the load or use a larger drive.

oL1: Overload 1 (oL1), internal electronic overload trip; GS3 LCD text: THERMAL OVERLOAD

What it means: The drive's electronic motor overload protection tripped.^{[7][8][10][11][13][14]}

Likely causes

• Motor overloaded
• Electronic thermal overload setting wrong
• Motor too small for the job
• Motor Rated Current P0.01 set lower than the real running current

First checks, in this order

1. Check for motor overload.
2. Check the electronic thermal overload setting (GS3: P6.00).
3. Check Motor Rated Current P0.01 against the nameplate.
4. Use a larger motor if needed.

oL2: Overload 2 (oL2), over-torque; GS3 LCD text: OVER-TORQUE

What it means: Over-torque detection tripped: current stayed above the detection level for longer than the detection time.^{[7][8][10][11][13][14]}

Likely causes

• Motor overloaded or the machine jammed
• Over-torque detection level or time set too low

First checks, in this order

1. Reduce the motor load and look for a jam.
2. Check P6.07 (detection mode), P6.08 (level) and P6.09 (time).

oH1: IGBT overheating (oH1); GS4-KPD text: IGBT Over Heat

What it means: The IGBT (power module) temperature is above its limit. GS10/GS20 first show an oH1 warning at the P06.15 level and trip at about 5 °C above the model default. The fault resets only after the IGBT cools about 10 °C below the trip level.^{[1][2][3][4][5][6]}

Likely causes

• High ambient or cabinet temperature
• Blocked vents or dirty heat sink
• Cooling fan failed
• Heat sources such as braking resistors close by
• Heavy load or high carrier frequency

First checks, in this order

1. Check the ambient temperature.
2. Clean the heat sink and vents and check the cooling fan.
3. Increase spacing around the drive or add cabinet cooling.
4. Reduce the load or the carrier frequency.
5. Use a larger drive if it keeps happening.

oH2: Heatsink overheating (oH2); GS4-KPD text: Cap Over Heat

What it means: Capacitor area temperature is too high because the heatsink is overheating.^[5]

Likely causes

• High ambient temperature
• Heatsink blocked
• Fan not running
• Too little clearance around the drive

First checks, in this order

1. Check the ambient temperature.
2. Clear any blockage at the heatsink.
3. Check that the fan runs.
4. Check ventilation clearance around the drive.

oH: Overheat (oH); GS3 LCD text: OVER-TEMPERATURE

What it means: The drive temperature sensor detected excessive heat.^{[7][8][9][10][11][12][13][14]}

Likely causes

• Ambient temperature above the drive rating
• Blocked ventilation holes
• Dirty heat sink fins or foreign objects on the heat sink
• Not enough space around the drive

First checks, in this order

1. Check that the ambient temperature is within range.
2. Clear the ventilation holes.
3. Clean the heat sink fins.
4. Leave enough space around the drive for air flow.

oH3: Motor overheating (oH3); GS4-KPD text: Mtr Overheat-PTC

What it means: The motor PTC thermistor input (or a PT100 input on the GS20) is above its trip level. On GS10/GS20, P06.29 sets the reaction (warn and run, fault and ramp stop, fault and coast, or no warning) and P06.30 sets the PTC level (default 50%). GS4 uses PTC level P6.40.^{[1][2][3][4][5][6]}

Likely causes

• Motor overloaded or shaft locked
• Motor fan failed or cooling surfaces dirty
• High ambient temperature
• Long running at low speed
• PTC sensor wiring fault
• Motor rated current entered wrong

First checks, in this order

1. Check that the motor is not jammed and the load is normal.
2. Check the motor fan and clean the motor.
3. Check the PTC wiring to the drive.
4. Check the motor rated current setting.
5. GS10/GS20: check P06.29 and P06.30. GS4: check P6.40.

tH1o: IGBT temperature detection failure (tH1o); GS4-KPD text: Thermister1 Open

What it means: The IGBT temperature sensor reads open or faulty (broken NTC or its wiring).^{[1][2][3][4][5]}

Likely causes

• Internal temperature sensor or its wiring failed

First checks, in this order

1. Wait 10 minutes, then cycle power.
2. If tH1o returns, contact AutomationDirect Technical Support. The GS4 manual says to replace the drive.

orP: Phase loss protection (orP); GS4 writes OrP, keypad text: Input Phase loss

What it means: DC bus ripple is too high while output current is above 50% of rating, which points to a missing or unbalanced input phase. GS10/GS20 use P06.53 for this protection.^{[1][2][3][4][5]}

Likely causes

• Missing input phase or blown input fuse
• Loose input terminals or damaged input cable
• Single-phase supply on a three-phase model
• Unbalanced three-phase supply

First checks, in this order

1. Check all three input phases and the input fuses (GS4 40 hp and up: check the AC input fuse).
2. Tighten the input terminal screws to the specified torque.
3. Check that a three-phase model is not fed from a single-phase supply.
4. Measure for supply voltage unbalance.

PHL: Phase loss (PHL), input phase loss warning; GS4-KPD text: Phase Loss Warn

What it means: Warning that an input phase is missing or weak. On the GS20 it clears by itself once the drive stops.^[1][5]

Likely causes

• Loose input terminal
• Broken input cable or failed main contactor
• Unbalanced three-phase supply

First checks, in this order

1. Check the input wiring, fuses and main contactor.
2. Tighten the terminal screws to the specified torque.
3. Check the three-phase supply for unbalance.

PHL: Input power 3-phase loss (PHL); GS3 LCD text: INPUT POWER LOSS

What it means: One phase of the input power is lost.^{[10][12][13][14][15]}

Likely causes

• Poor connection on the input power line
• Lost phase on the supply

First checks, in this order

1. Check the input power connections.
2. Check the supply for a missing phase.

oPL1: Output phase loss U phase (oPL1)

What it means: The drive sees no current in output phase U. oPL2 and oPL3 are the same check for phases V and W. P06.45 sets the reaction: warn and run, fault and ramp stop, fault and coast, or no warning.^[1][2][3][4]

Also on: GS4 shows output phase loss as UPHL, VPHL and WPHL

Likely causes

• Broken or loose motor lead
• Unbalanced motor windings
• Single-phase motor on a three-phase drive
• Loose flat cable on the control board
• Drive and motor sizes badly mismatched

First checks, in this order

1. Check the motor cable and its connections.
2. Check the motor windings for unbalance with a meter.
3. Measure the three output currents with a clamp meter.
4. Check P06.45 to P06.47.
5. If the currents are balanced and the fault stays, contact AutomationDirect Technical Support.

ocS: Over-current at stop (ocS); GS4-KPD text: OC at Stop

What it means: GS10/GS20: over-current, or a hardware failure in current detection, while the drive is stopped. The GS4 manual describes it as a hardware failure in current detection.^{[1][2][3][4][5]}

Likely causes

• Current sensing hardware fault
• Electrical noise from poor wiring or grounding

First checks, in this order

1. Cycle power.
2. Check control and main circuit wiring and grounding for noise.
3. If cd1, cd2 or cd3 appears after the power cycle, the drive needs repair. GS4: replace the drive.

occ: IGBT short circuit (occ); GS4-KPD text: IGBT Short Ckt; GS3 LCD text: OUTPUT SHORTED

What it means: A short was detected between the upper and lower IGBT of the output bridge, an internal power stage failure.^{[5][6][13][14][15]}

Likely causes

• Failed IGBT in the drive output stage

First checks, in this order

1. Disconnect the motor and check the motor and cable so a new drive is not damaged the same way.
2. GS4: replace the drive; if it is under warranty, contact AutomationDirect Returns.
3. GS3: contact AutomationDirect support.

ot1: Over torque 1 (ot1); GS4-KPD text: Over Torque 1

What it means: Output current stayed above over-torque level 1 for longer than the detection time. GS10/GS20: level P06.07, time P06.08, action P06.06 (1 or 3 warns, 2 or 4 trips). GS4: level P6.15, time P6.16, mode P6.14.^{[1][2][3][4][5]}

Likely causes

• Jam, binding or a failed bearing in the machine
• Load too heavy for the motor
• Detection level or time set too low
• Acceleration or deceleration too fast

First checks, in this order

1. Look for a mechanical jam or failure and clear it.
2. Check the over-torque level and time parameters.
3. Reduce the load or use a larger motor.
4. Check the motor rated current setting (GS4: P0.01).

ot2: Over torque 2 (ot2); GS4-KPD text: Over Torque 2

What it means: Same as ot1, using the second over-torque setting. GS10/GS20: action P06.09, level P06.10, time P06.11. GS4: mode P6.17, level P6.18, time P6.19.^{[1][2][3][4][5]}

Likely causes

• Jam or binding in the machine
• Load too heavy
• Detection level or time set too low

First checks, in this order

1. Look for a mechanical jam and clear it.
2. Check the over-torque 2 parameters.
3. Reduce the load or use a larger motor.

uC: Under current (uC); GS4-KPD text: Under Current

What it means: Output current dropped below the low-current level, which often means the load has come off the motor. GS10/GS20: level P06.71, time P06.72, action P06.73 (3 only warns). GS4: P6.52 to P6.54.^{[1][2][3][4][5]}

Likely causes

• Load lost, for example a broken belt or coupling
• Motor cable not connected properly
• Under-current settings wrong for the application

First checks, in this order

1. Check the motor cable connections.
2. Check that the load is really connected to the motor.
3. Check the under-current parameters.

EF: External fault (EF); GS4-KPD text: External Fault

What it means: A digital input set as External Fault turned on (GS10/GS20: input setting 10). The drive stops as set in P07.20 (coast or one of the decel times).^{[1][2][3][4][5]}

Likely causes

• An outside device (safety relay, level switch, interlock) opened or closed the EF input
• Wiring fault on the EF input

First checks, in this order

1. Find the device wired to the EF input and fix its fault.
2. Check the input wiring.
3. Press RESET once the input is back to normal.

EF: External Fault (EF); GS3 LCD text: EXTERNAL FAULT

What it means: The external fault input (EF to CM) went from off to on. On the GS2 the same code also shows if the 4 to 20 mA analog signal is lost.^{[7][8][10][11][13][14]}

Likely causes

• Outside device closed the EF input
• 4 to 20 mA analog input signal lost (GS2)

First checks, in this order

1. Check the device wired to the EF input and clear its signal.
2. GS2: check the 4 to 20 mA analog input signal.
3. Reset from the keypad or input terminal.

EF1: Emergency stop (EF1); GS4-KPD text: Emergency Stop

What it means: A digital input set as Emergency Stop turned on (GS10/GS20: input setting 28). The drive cuts its output at once and the motor coasts.^{[1][2][3][4][5]}

Likely causes

• E-stop button or safety circuit opened
• Wiring fault on the emergency stop input

First checks, in this order

1. Find why the emergency stop circuit operated.
2. Restore the input, make sure the machine is safe, then press RESET.

bb: External base block (bb); GS4-KPD text: Base Block

What it means: A digital input set as Base Block is on (GS10/GS20: input setting 11), so the drive turns off its output and the motor coasts. The GS20 does not save bb in the fault record.^{[1][2][3][4][5]}

Likely causes

• Base block input switched on by a control circuit
• Wiring fault on that input

First checks, in this order

1. Check the device or switch driving the base block input.
2. Turn the input off, check the system is normal, then press RESET.

bb: External Base-Block (bb); GS3 LCD text: EXT. BASE-BLOCK

What it means: The external base-block input is active, so the drive output is turned off. Releasing the input lets the drive run again.^{[7][8][10][11][13][14]}

Likely causes

• Base-block input switched on by a control circuit

First checks, in this order

1. Check what is driving the base-block input.
2. Deactivate the input to run again.

CE1: Illegal command (CE1); GS4-KPD text: PC Cmd Error

What it means: The Modbus master sent a function code the drive does not accept (the drive accepts 03, 06, 10 and 63). On GS10/GS20 it is only a warning when P09.02 = 0; GS4 lists it as both warning and fault.^{[1][2][3][4][5]}

Likely causes

• Wrong function code in the master program
• Communication settings not matching the master
• Electrical noise on the RS-485 line

First checks, in this order

1. Check the command the master is sending.
2. Check that P09.04 (GS4: communication settings) matches the master.
3. Check RS-485 wiring and grounding, and run it apart from power wiring.
4. Replace a damaged cable.

CE2: Illegal data address (CE2); GS4-KPD text: PC Address Error

What it means: The Modbus master tried to read or write a register address the drive does not have.^{[1][2][3][4][5]}

Likely causes

• Wrong register address in the master program
• Address offset mix-up between the master and the drive

First checks, in this order

1. Check the register addresses in the master against the drive manual.
2. Check communication settings (P09.04) and RS-485 wiring.

CE3: Illegal data value (CE3); GS4-KPD text: PC Data Error

What it means: The Modbus data value or data length sent to the drive is out of range.^{[1][2][3][4][5]}

Likely causes

• Value above the maximum or below the minimum for that parameter
• Message data too long

First checks, in this order

1. Check the value the master writes against the parameter range.
2. Check communication settings and wiring.

CE4: Data is written to read-only address (CE4); GS4-KPD text: PC Slave Fault

What it means: The Modbus master tried to write to a read-only register.^{[1][2][3][4][5]}

Likely causes

• Master program writing to a status or read-only address

First checks, in this order

1. Check that the master writes only to writable parameter addresses.
2. Check communication settings and wiring.

CE10: Modbus transmission time-out (CE10); GS4-KPD text: PC TimeOut

What it means: No valid Modbus message arrived within the time-out. GS10/GS20: time-out P09.03, reaction P09.02 (0 warns and keeps running). GS4: active only when P9.03 is not 3 and P9.05 is not 0; the time is P9.05.^{[1][2][3][4][5]}

Likely causes

• Master (PLC, HMI or PC) stopped polling or polls too slowly
• Broken or noisy RS-485 cable
• Communication settings not matching

First checks, in this order

1. Make sure the master sends messages faster than the time-out setting.
2. Check RS-485 wiring and grounding.
3. Check that P09.01 and P09.04 match the master.
4. Replace a damaged cable.

Ce01: Communications Warning: Illegal command code (Ce01)

What it means: The command code in the Modbus message is not one the drive supports.^[7][10][13]

Also on: GS3 LCD shows Invalid Cmd Code

Likely causes

• Wrong function code in the master program

First checks, in this order

1. Check the function code the master sends.
2. P9.03 Transmission Fault Treatment sets the reaction: 0 display and keep running (default), 1 display and ramp to stop, 2 display and coast to stop, 3 no display and keep running.

Ce02: Communications Warning: Illegal data address (Ce02)

What it means: The data address in the Modbus message is not available on the drive.^[7][10][13]

Also on: GS3 LCD shows Invalid Address

Likely causes

• Wrong register address in the master program

First checks, in this order

1. Check the register address against the drive's Modbus address table.
2. Check P9.03 for how the drive reacts.

Ce03: Communications Warning: Illegal data value (Ce03)

What it means: The data value in the Modbus message is not valid for the drive.^[7][10][13]

Also on: GS3 LCD shows Invalid Data

Likely causes

• Value outside the parameter range

First checks, in this order

1. Check the value the master writes against the parameter range.
2. Check P9.03 for how the drive reacts.

Ce04: Communications Warning: Slave device failure (Ce04)

What it means: The drive cannot perform the action the Modbus master asked for.^[7][10][13]

Also on: GS3 LCD shows Slave Comm Fault

Likely causes

• Request the drive cannot carry out in its present state

First checks, in this order

1. Check what the master is asking the drive to do and when.
2. Check P9.03 for how the drive reacts.

AFE: PID loss AI2 (AFE); GS10: PID loss AI-V; GS4-KPD text: PID Fbk Loss

What it means: The PID feedback signal was lost while PID control is on. GS20 checks a 4 to 20 mA input for less than 4 mA. GS10/GS20: P08.09 sets warn and run, fault and ramp stop, fault and coast, or warn and run at the last frequency.^{[1][2][3][4][5]}

Likely causes

• Feedback transmitter failed
• Broken feedback wire or loose terminal

First checks, in this order

1. Check the feedback cable and tighten the terminals.
2. Check the feedback device and replace it if failed.
3. GS10/GS20: check P08.09. GS4: check the PID parameter settings.

FbE: PID Feedback Loss (FbE); GS3 LCD text: PID FBACK LOSS

What it means: The 4 to 20 mA PID feedback signal has been lost. P7.27 sets the reaction: 00 warn and stop the drive (default), 01 warn and keep running.^{[10][11][13][14][15]}

Likely causes

• Feedback transmitter failed or lost power
• Broken feedback wiring

First checks, in this order

1. Check the 4 to 20 mA feedback wiring and transmitter.
2. Check P7.27.

ACE: AI2 loss (ACE); GS10: AI-C loss; GS4-KPD text: Analog Loss Err

What it means: A 4 to 20 mA analog input dropped below 4 mA. On GS10/GS20, P03.19 = 3 trips with ACE; settings 1 and 2 only warn and show ANL. On GS4, P4.63 or P4.64 must be set to 3 for this fault.^{[1][2][3][4][5]}

Likely causes

• Broken analog signal wire
• Transmitter or outside device failed

First checks, in this order

1. Check the analog cable and tighten the terminals.
2. Check the outside device and replace it if failed.
3. Check P03.19 (GS4: P4.63, P4.64).

AUE: Auto-tuning error (AUE); GS4-KPD text: Auto Tuning Err

What it means: Motor auto-tuning did not complete.^{[1][2][3][4][5]}

Likely causes

• STOP pressed during auto-tune
• Wrong motor data entered
• Motor not wired or an output contactor open
• Locked shaft or load too heavy

First checks, in this order

1. Run auto-tune again without pressing STOP.
2. GS10/GS20: set the motor data P01.01 and P01.02 correctly and set P01.00 above the motor rated frequency.
3. Check the motor wiring and that any output contactor is closed.
4. GS4: check the drive to motor cabling and try again.

cFA: Auto accel/decel failure (cFA); GS3 LCD text: AUTO RAMP FAULT

What it means: The automatic acceleration/deceleration function failed.^{[7][8][10][11][13][14]}

Likely causes

• Auto accel/decel unable to handle the load

First checks, in this order

1. GS1/GS2: stop using auto acceleration/deceleration.
2. GS3: treat it like an over-current or over-voltage trip and check those causes.

oSL: Over slip error (oSL); GS4-KPD text: Over Slip Error

What it means: Motor slip stayed above the limit for longer than allowed (induction motors). GS10/GS20: level P07.29, time P07.30, reaction P07.31 (0 warns), maximum slip P10.29. GS4: P2.26 and P2.27.^{[1][2][3][4][5]}

Likely causes

• Motor overloaded
• Motor parameters wrong
• Slip limits set too tight

First checks, in this order

1. Check the motor parameters against the nameplate.
2. Reduce the load if the motor is overloaded.
3. Check the over slip parameters.

dEb: Deceleration energy backup error (dEb); GS4-KPD text: DEB Error

What it means: The power loss ride-through function acted: after a power dip the DC bus fell below the dEb level and the motor ramped to stop. Active when P07.13 is not 0 (GS4: P6.61).^[1][2][3][5]

Also on: GS10 lists dEb as a warning (ID 102)

Likely causes

• Unstable supply or a short outage
• A large load on the same supply pulling the voltage down

First checks, in this order

1. Check the supply for dips and outages.
2. Move large loads to another supply or increase supply capacity.
3. GS4: set P6.61 to 0 if this function is not wanted.

STo: STO (STo), Safety Torque Off function active; GS4 writes STO

What it means: The Safe Torque Off inputs are open, so the drive cannot produce torque.^[1][2][5]

Likely causes

• Safety circuit opened the STO inputs
• STO jumper or wiring loose
• Onboard +24V shorted to DCM (GS4)

First checks, in this order

1. Close the STO1/SCM1 and STO2/SCM2 circuits and cycle power.
2. Check the control terminal connections.
3. GS20: P06.44 = 1 resets by itself when the inputs return; P06.44 = 0 latches until a reset.
4. GS4: see Appendix E of the manual.

cF1: CPU failure 1 (cF1), internal memory IC cannot be programmed; GS3 LCD text: CPU FAILURE 1

What it means: The drive could not write to its internal memory.^{[7][8][10][11][13][14]}

Likely causes

• Input voltage out of range
• Internal memory fault

First checks, in this order

1. Switch off power.
2. Check that the input voltage is within the drive rating.
3. Switch the drive back on. If it stays, contact AutomationDirect support.

cF2: CPU failure 2 (cF2), internal memory IC cannot be read; GS3 LCD text: CPU FAILURE 2

What it means: The drive could not read its internal memory.^{[7][8][10][11][13][14]}

Likely causes

• Loose connection between the main control board and the power board
• Corrupt parameter memory

First checks, in this order

1. GS1/GS2: check the connections between the main control board and the power board.
2. Reset the drive to factory defaults (GS3: P9.08 = 99).
3. Cycle power. If it stays, contact AutomationDirect support.

cF3: CPU failure 3 (cF3); GS3 LCD text: CPU FAILURE 3

What it means: Internal drive circuitry is abnormal (GS3: the internal memory IC did not receive output status).^{[7][8][10][11][13][14]}

Likely causes

• Input voltage out of range
• Internal circuit fault

First checks, in this order

1. Switch off power.
2. Check the input voltage and the connections at L1, L2 and L3.
3. Switch the drive back on. If it stays, contact AutomationDirect support.

cF2: EEPROM read error (cF2); GS4-KPD text: EEPROM Read Err

What it means: The drive cannot read its internal EEPROM.^{[1][2][3][4][5][6]}

Likely causes

• Corrupt parameter memory
• Internal memory fault

First checks, in this order

1. Press RESET or reset the parameters to defaults.
2. Cycle power.
3. If it stays, contact AutomationDirect Technical Support. GS4: replace the drive.

cF1: Internal EEPROM can not be programmed (cF1); GS4-KPD text: EEPROM Write Err

What it means: The GS4 cannot write to its internal EEPROM.^[5]

Likely causes

• Internal memory fault

First checks, in this order

1. Reset to factory settings.
2. If it stays, replace the drive; if under warranty, contact AutomationDirect Returns.

HPF: Hardware Protection Failure (HPF); GS3 LCD text: HARDWARE FAILURE

What it means: The drive's hardware protection circuit failed.^{[7][8][9][10][11][12][13][14]}

Likely causes

• Internal hardware fault
• Supply problem on L1, L2, L3 (GS3)

First checks, in this order

1. GS3: check all connections and the voltage at L1, L2 and L3.
2. Contact AutomationDirect support; the GS1 and GS2 manuals say to return the drive to the factory.

codE: Software protection failure (codE)

What it means: The drive's software protection failed.^{[7][8][9][10][11][12]}

Likely causes

• Internal firmware fault

First checks, in this order

1. Cycle power once to confirm it repeats.
2. Contact AutomationDirect support; the manuals say to return the drive to the factory.

cd1: U-phase error (cd1); GS4-KPD text: Amp Err: U Phase

What it means: U-phase current sensing failed its check at power up. cd2 (V phase) and cd3 (W phase) mean the same for the other phases.^{[1][2][3][4][5]}

Likely causes

• Current sensor or its circuit inside the drive failed

First checks, in this order

1. Cycle power and let the capacitors discharge between tries.
2. If it keeps showing, contact AutomationDirect Technical Support; the GS4 manual says the drive most likely needs repair or replacement.

Pcod: Password is locked (Pcod); GS4-KPD text: Password Error

What it means: A wrong password was entered three times in a row, so the keypad is locked.^{[1][2][3][4][5]}

Likely causes

• Wrong password entered (GS10/GS20: P00.07)

First checks, in this order

1. Cycle power and enter the correct password.
2. GS10/GS20 forgotten password: enter 9999 and press ENTER, then do it again within 10 seconds. This returns all parameters to default.
3. GS4: see P8.06 and P8.07.

bF: Brake resistor fault (bF); GS4-KPD text: Braking Fault

What it means: The GS4 detected a fault in its braking circuit.^[5]

Likely causes

• Brake resistor or braking circuit problem

First checks, in this order

1. Check the brake resistor and its wiring.
2. Press RESET. If bF stays, the manual says to return the drive to the factory.

ENCODER LOSS: Encoder Feedback Loss (ENCODER LOSS)

What it means: Encoder feedback was lost. P10.05 = 1 or 2 stops the drive and records the fault; P10.05 = 0 warns and keeps running.^[13][14][15]

Likely causes

• Encoder board without power
• Encoder miswired or damaged
• Wrong encoder voltage or setup

First checks, in this order

1. Check that the encoder feedback board has power.
2. Check the encoder wiring.
3. Check the encoder voltage and setup.
4. Check the encoder mechanically and electrically.

MOM POWER LOSS: Momentary Power Loss (MOM POWER LOSS)

What it means: Input power to the drive was lost for a moment.^[13][14][15]

Likely causes

• Supply dip or short outage
• Loose input power connection

First checks, in this order

1. Check the line power to the drive.
2. Check the input connections.