Omron Servo Error Codes

16.0 / 16.00: Overload (G5) / Overload Error (1S)

What it means: The drive's electronic thermal protection tripped: motor torque (current) stayed above the overload level for too long.^[1][2][3]

Also on: R88D-KT and R88D-KN-ECT show 16.0; 1S shows Er 16 00.

Drive response: servo off; can be reset after the cause is removed (R88D-KN-ECT: not within 10 s of the trip)

Likely causes

• Load too heavy, effective torque above rated torque for too long
• Acceleration or deceleration too short for the load
• Vibration or hunting from poor gain tuning or a wrong inertia ratio
• Motor cable wired wrong or broken
• Machine jammed, hit an object or got heavier suddenly (friction, distortion)
• Holding brake not releasing
• Multi-axis machine: motor cable of one axis connected to another axis

First checks, in this order

1. Watch the torque (current) waveform in CX-Drive or Sysmac Studio: look for oscillation and check the load ratio and overload warning A0.
2. Lengthen the acceleration and deceleration times, reduce the load, or move to a larger drive and motor.
3. Retune the gain and check the inertia ratio (Pn004 on R88D-KT, 3004 hex on R88D-KN-ECT).
4. Measure the voltage at the brake terminals and confirm the brake releases at servo on.
5. Confirm the U, V, W cable and the encoder cable go to the same motor and axis.
6. Overload level setting: Pn512 (R88D-KT) or 3512 hex (R88D-KN-ECT).
7. Sysmac Studio event code: 38810000 hex (1S), 34E20000 hex (R88D-KN-ECT).

24.0 / 24.00: Error Counter Overflow (G5) / Excessive Position Deviation Error (1S)

What it means: The position error (following error) between the command and the actual motor position grew past the allowed limit.^[1][2][3]

Also on: 1S shows Er 24 00.

Drive response: servo off; can be reset after the cause is removed

Likely causes

• Motor cannot follow the command: torque saturated, load too heavy or mechanism binding
• Acceleration too fast for the machine
• Gain too low
• Torque limit set too low
• Limit value too small for the application
• Encoder wiring fault

First checks, in this order

1. Check that the motor really turns as commanded and look at the torque monitor for saturation.
2. Adjust the gain.
3. Set the torque limits to maximum: Pn013 and Pn522 (R88D-KT), 60E0 hex and 60E1 hex (R88D-KN-ECT).
4. Lengthen the acceleration and deceleration times, or reduce the load and speed.
5. Check the encoder wiring against the wiring diagram.
6. Only then raise the limit: Error Counter Overflow Level Pn014 (R88D-KT) or Following error window 6065 hex (R88D-KN-ECT and 1S).
7. Sysmac Studio event code: 38830000 hex (1S), 34E40000 hex (R88D-KN-ECT).

21.0 / 21.00: Encoder Communications Disconnection Error

What it means: The drive lost communication with the motor encoder (1S: four timeouts in a row).^[1][2][3]

Also on: 1S shows Er 21 00.

Drive response: servo off; cannot be reset, cycle the power (1S: or Unit Restart 2400 hex)

Likely causes

• Encoder cable unplugged, broken or wired to the wrong pins
• Loose encoder connector or poor contact
• Electrical noise on the encoder cable
• Encoder supply voltage too low (long cable)
• Encoder failure

First checks, in this order

1. Reseat the encoder connector at the drive (CN2) and at the motor.
2. Test the cable for breaks with it disconnected at both ends.
3. Separate the motor power cable from the encoder cable, connect the shield to FG and check the motor ground wire goes to FG.
4. Use the Omron recommended encoder cable; on G5 the encoder needs 5 VDC +/-5% (4.75 to 5.25 V), watch long runs.
5. If it keeps coming back with good wiring, replace the motor (encoder).
6. Sysmac Studio event code: 084A0000 hex (1S), 08080000 hex (R88D-KN-ECT).

21.1 / 21.01: Encoder Communications Error

What it means: The encoder cable is connected but the data from the encoder is corrupted, mostly by noise (1S: bad data four times in a row).^[1][2][3]

Also on: 1S shows Er 21 01 (the manual's own display example).

Drive response: servo off; cannot be reset, cycle the power (1S: or Unit Restart 2400 hex)

Likely causes

• Noise on the encoder cable
• Encoder and motor power cables bundled together
• Shield or ground not connected
• Encoder supply voltage too low
• Poor contact in the encoder connector

First checks, in this order

1. Separate the encoder cable from the motor power cable.
2. Connect the shield to FG and the motor ground wire to FG.
3. Check the encoder supply (G5: 5 VDC +/-5%), especially on long cables.
4. Reseat or replace the encoder cable; use the recommended cable.
5. Sysmac Studio event code: 084B0000 hex (1S), 08090000 hex (R88D-KN-ECT).

14.0 / 14.00: Overcurrent (G5) / Overcurrent Error (1S)

What it means: Current through the power stage went above the protection level.^[1][2][3]

Also on: 1S shows Er 14 00.

Drive response: servo off; cannot be reset, cycle the power (1S: or Unit Restart 2400 hex)

Likely causes

• Short circuit between U, V and W or ground fault in the motor cable
• Motor winding burned or insulation failed
• Loose or missing motor connector pins
• Dynamic brake relay welded from frequent servo on/off (G5)
• Motor not matched to the drive
• Command given at the same time as or before servo on (G5)
• External regeneration resistor shorted or below the minimum resistance
• Noise (1S) or drive failure

First checks, in this order

1. Disconnect the motor cable and turn the servo on: if it trips at once, the drive is faulty.
2. Check insulation from U, V and W to the motor ground wire with the motor disconnected from the drive; replace the motor if it is low.
3. Compare the resistance of the three motor phases; unbalance means a bad motor.
4. Check the motor connector pins and the regeneration resistor wiring and value.
5. Check the drive and motor nameplates match; on G5 wait at least 100 ms after servo on before giving commands.
6. After a dynamic brake stop, wait at least 10 minutes before servo on (G5).
7. Sysmac Studio event code: 08490000 hex (1S), 04AC0000 hex (R88D-KN-ECT).

12.0 / 12.00: Overvoltage (G5) / Overvoltage Error (1S)

What it means: The DC bus (P to N) voltage went too high. On G5 the trip is about 200 VDC on 100 V models, 400 VDC on 200 V models and 800 VDC on 400 V models.^[1][2][3]

Also on: 1S shows Er 12 00.

Drive response: servo off; G5: can be reset after the cause is removed; 1S: cycle the power or run Unit Restart (2400 hex)

Likely causes

• Supply voltage too high
• Voltage surge from a phase advance capacitor or a UPS
• Regeneration resistor wiring broken
• Regeneration resistor too small for the braking energy (large inertia, heavy vertical axis)
• External regeneration resistor not set up in the drive parameters (1S)
• Drive circuit failure

First checks, in this order

1. Measure the line voltage at L1, L2 and L3.
2. Remove any phase advance capacitor on the drive supply.
3. Measure the external resistor across B1 and B2 with power off; infinite means a break, replace it.
4. Calculate the regenerative energy and fit a large enough external regeneration resistor; slow the descent or deceleration.
5. 1S: set the regeneration parameters (4310 hex) to the resistor actually fitted.
6. Sysmac Studio event code: 08410000 hex (1S), 04A90000 hex (R88D-KN-ECT).

11.0: Control Power Supply Undervoltage

What it means: The control circuit DC voltage dropped below its limit (about 70 VDC on 100 V models, 145 VDC on 200 V models, 15 VDC on 400 V models with 24 VDC control).^[1][2]

Also on: R88D-KT and R88D-KN-ECT.

Drive response: servo off; can be reset; not stored in the alarm history

Likely causes

• Control supply voltage low or a momentary power dip
• Supply too small: voltage sagged from inrush when the main power came on
• Drive circuit failure

First checks, in this order

1. Measure the voltage at L1C and L2C (24 VDC input on 400 V models).
2. Raise the supply voltage or capacity, or change the power supply.
3. If the supply is good, replace the drive.
4. Sysmac Studio event code: 04A80000 hex (R88D-KN-ECT).

13.0 / 13.00: Main Power Supply Undervoltage (insufficient voltage between P and N)

What it means: The main circuit DC voltage fell too low while the servo was on (G5: about 80 VDC on 100 V, 110 VDC on 200 V, 180 VDC on 400 V models).^[1][2][3]

Also on: 1S shows Er 13 00.

Drive response: servo off; can be reset after the cause is removed; G5 does not store it in the alarm history

Likely causes

• Main supply voltage low or the main contactor dropped out
• Momentary power loss longer than the Momentary Hold Time
• Supply too small for the inrush current
• Main power cables not connected to L1, L2, L3 (1S)
• Noise between several drives on the same supply (1S)
• Drive failure

First checks, in this order

1. Measure the voltage at L1, L2 and L3 under load.
2. Check the main circuit contactor and its control.
3. Check the Momentary Hold Time: Pn509 (R88D-KT), 3509 hex (R88D-KN-ECT), 4320-01 hex (1S); on G5 this error also depends on Undervoltage Error Selection (Pn508 or 3508 hex).
4. 1S with several drives: do not bundle motor power cables, keep main supply wiring short, one noise filter per drive.
5. Sysmac Studio event code: 08480000 hex (1S), 04AA0000 hex (R88D-KN-ECT).

13.1: Main Power Supply Undervoltage (AC cutoff detected)

What it means: The drive detected that the main circuit AC supply was cut off.^[1][2]

Also on: R88D-KT and R88D-KN-ECT.

Drive response: servo off; can be reset; not stored in the alarm history

Likely causes

• Momentary power interruption
• Supply capacity too small for the inrush current
• Phase loss: a 3-phase drive running on single-phase power
• Drive failure

First checks, in this order

1. Check the Momentary Hold Time (Pn509 or 3509 hex).
2. Check that all phases are connected; for single-phase 100 V or 200 V use L1 and L3.
3. Increase the supply capacity.
4. Sysmac Studio event code: 04AB0000 hex (R88D-KN-ECT).

15.0 / 15.00: Servo Drive Overheat

What it means: The drive heatsink or power element temperature went over its limit.^[1][2][3]

Also on: 1S shows Er 15 00.

Drive response: servo off; G5: cannot be reset, cycle the power; 1S: can be reset after it cools

Likely causes

• Cabinet or ambient temperature too high
• Poor cooling or blocked airflow
• Drive overloaded

First checks, in this order

1. Measure the temperature around the drive and improve cooling and spacing in the cabinet.
2. Lengthen the acceleration, deceleration or stop times and lighten the load.
3. If needed, use a larger drive and motor.
4. Sysmac Studio event code: 38800000 hex (1S), 34E10000 hex (R88D-KN-ECT).

18.0 / 18.00: Regeneration Overload (G5) / Regeneration Overload Error (1S)

What it means: The braking (regenerative) energy is more than the regeneration resistor can absorb.^[1][2][3]

Also on: 1S shows Er 18 00.

Drive response: servo off; cannot be reset, cycle the power (1S: or Unit Restart 2400 hex)

Likely causes

• Large load inertia decelerating fast
• Speed too high to stop within the deceleration time
• Built-in resistor used for continuous regenerative braking
• External resistor limited to 10% duty (G5 setting)
• Regeneration settings not matched to the resistor (1S)
• Supply voltage above spec or failed resistor (1S)

First checks, in this order

1. Check the regeneration load ratio and the A1 warning history.
2. Lengthen the deceleration and stop times or lower the speed.
3. Fit an external regeneration resistor, or a larger drive and motor.
4. G5: check Regeneration Resistor Selection (Pn016 or 3016 hex); setting 2 removes the protection, so fit a thermal switch.
5. 1S: set the regeneration parameters (4310 hex) to the resistance actually fitted.
6. Sysmac Studio event code: 38820000 hex (1S), 34E30000 hex (R88D-KN-ECT).

38.0 / 38.00: Drive Prohibition Input Error (R88D-KN-ECT: Drive Prohibition Input Error 1)

What it means: Both drive prohibition (overtravel) inputs POT and NOT were active at the same time (G5 with Pn504 or 3504 hex set to 2: either one).^[1][2][3]

Also on: R88D-KN-ECT also has 38.1 Drive Prohibition Input Error 2 (overtravel input during a CX-Drive test run or FFT). 1S shows Er 38 00.

Drive response: servo off; can be reset after the cause is removed; G5 does not store it in the alarm history

Likely causes

• Limit switch fault or both limits made
• Broken or wrong wiring on POT or NOT
• Control I/O supply (12 to 24 VDC) rising too slowly at power on
• Wrong drive prohibition input or logic settings

First checks, in this order

1. Check the forward and reverse limit switches, wiring and their 12 to 24 VDC supply.
2. Check that the I/O supply comes up quickly at power on.
3. Check Drive Prohibition Input Selection: Pn504 (R88D-KT) or 3504 hex (R88D-KN-ECT); on 1S check the drive prohibition input port and logic settings.
4. Sysmac Studio event code: 64E30000 hex (1S), 64E00000 hex (R88D-KN-ECT).

26.0 / 26.00: Overspeed (G5) / Excessive Speed Error (1S)

What it means: Motor speed went above the overspeed detection level.^[1][2][3]

Also on: 1S shows Er 26 00.

Drive response: servo off; can be reset after the cause is removed

Likely causes

• Speed command too high or electronic gear set wrong
• Command pulse frequency or multiplier wrong (R88D-KT)
• Overshoot from poor gain tuning
• Motor driven by an external force (1S)
• Encoder wiring fault (G5)

First checks, in this order

1. Check the commanded speed and the electronic gear ratio.
2. R88D-KT: check the command pulse frequency, dividing and multiplication ratio.
3. Retune the gain if the speed overshoots.
4. Check whether gravity or the load is driving the motor.
5. Detection level: Pn513 (R88D-KT), 3513 hex (R88D-KN-ECT), 3B60-04 hex (1S).
6. Sysmac Studio event code: 38850000 hex (1S), 34E60000 hex (R88D-KN-ECT).

87.0 / 87.00: Emergency stop input error (R88D-KT) / Immediate Stop Input Error (R88D-KN-ECT) / Error Stop Input (1S)

What it means: The drive's stop input (STOP on G5, ESTP on 1S) is active.^[1][2][3]

Also on: 1S shows Er 87 00.

Drive response: servo off; can be reset after the input is released; G5 does not store it in the alarm history

Likely causes

• Emergency stop pressed or the external stop circuit opened
• Stop input wired wrong or broken

First checks, in this order

1. Find out why the stop circuit opened and release it.
2. Check the STOP or ESTP input wiring.
3. Reset only after the input is back to normal.
4. Sysmac Studio event code: 68220000 hex (1S), 64E20000 hex (R88D-KN-ECT).

40.0: Absolute Encoder System Down Error

What it means: The absolute encoder lost its backup: the built-in capacitor voltage fell because both the encoder supply and the battery were gone.^[1][2]

Also on: R88D-KT and R88D-KN-ECT with absolute encoder motors.

Drive response: servo off; can be reset only after the absolute encoder is cleared

Likely causes

• Battery flat or disconnected while the drive was off
• Encoder cable unplugged with the power off
• Battery cable or holder fault

First checks, in this order

1. Fit or replace the battery (look for earlier A2 battery warnings).
2. Perform the absolute encoder clear (setup) in CX-Drive or from the R88D-KT front panel, then reset.
3. Home the axis again: the multi-turn position is lost.
4. Sysmac Studio event code: 384D0000 hex (R88D-KN-ECT).

24.1 / 24.01: Excessive Speed Deviation Error (R88D-KN-ECT, 1S) / Excessive speed error (R88D-KT)

What it means: The difference between the commanded speed and the actual speed went past the set limit.^[1][2][3]

Also on: 1S shows Er 24 01.

Drive response: servo off; can be reset after the cause is removed

Likely causes

• Motor cannot follow: gain too low or acceleration too fast
• Shaft held back by an external force
• Limit set too small; an immediate stop from overtravel or halt makes the deviation jump

First checks, in this order

1. Improve tracking by adjusting the gain, or lengthen the acceleration time.
2. Check for mechanical binding or external forces on the shaft.
3. Raise the limit or set it to 0 to disable: Pn602 (R88D-KT), 3602 hex (R88D-KN-ECT), 3B60-05 hex (1S).
4. Sysmac Studio event code: 38840000 hex (1S), 34E50000 hex (R88D-KN-ECT).

14.1 / 14.01: IPM Error (G5) / Power Module Error (1S)

What it means: The power module reported a fault, usually a short or ground fault on the motor power lines.^[1][2][3]

Also on: 1S shows Er 14 01.

Drive response: servo off; cannot be reset, cycle the power (1S: or Unit Restart 2400 hex)

Likely causes

• Short circuit, ground fault or bad contact on the U, V or W motor cable
• Motor insulation failure
• External regeneration resistor shorted or too low in resistance
• Drive failure

First checks, in this order

1. Check the motor cable and connector for shorts and loose strands.
2. Check insulation from U, V and W to the motor ground wire with the motor disconnected from the drive.
3. Check the external regeneration resistor wiring and resistance.
4. If the motor side is good, replace the drive.
5. Sysmac Studio event code: 08390000 hex (1S), 04AD0000 hex (R88D-KN-ECT).

23.0: Encoder Communications Data Error

What it means: Communication with the encoder works, but the content of the data is wrong, mostly because of noise.^[1][2]

Also on: R88D-KT and R88D-KN-ECT.

Drive response: servo off; cannot be reset, cycle the power

Likely causes

• Noise on the encoder cable
• Encoder and motor power cables bundled together
• Encoder supply voltage too low on a long cable

First checks, in this order

1. Check the encoder supply is 5 VDC +/-5% (4.75 to 5.25 V).
2. Separate the encoder cable from the motor cable and connect the shield to FG.
3. Check the encoder cable connections.
4. Sysmac Studio event code: 080A0000 hex (R88D-KN-ECT).

30.0: Safety Input Error

What it means: At least one of the two safety inputs (safe torque off) turned off; the display flashes st.^[1][2]

Also on: R88D-KT and R88D-KN-ECT.

Drive response: servo off; can be reset once both safety inputs are on; not stored in the alarm history

Likely causes

• Safety circuit opened (door switch, safety relay, emergency stop)
• Broken or loose safety input wiring

First checks, in this order

1. Check the wiring of safety inputs 1 and 2 and the safety device driving them.
2. Reset only after both safety inputs are on again; resetting too early can give error 99.0.
3. Sysmac Studio event code: 080B0000 hex (R88D-KN-ECT).

99.0: Other errors

What it means: Catch-all error: the control circuit malfunctioned or the drive self-diagnosis found an internal fault. Other numbers not in the list are handled the same way.^[1][2]

Also on: R88D-KT and R88D-KN-ECT.

Drive response: servo off; cannot be reset, cycle the power

Likely causes

• Heavy electrical noise
• Internal drive fault found by self-diagnosis
• Error reset given while safety input 1 or 2 was still off
• R88D-KT: 11 V or more applied to analog input 2 or 3

First checks, in this order

1. Cycle the power.
2. Reset only when both safety inputs are on.
3. R88D-KT: check the voltage on analog inputs 2 and 3.
4. If it stays after a power cycle, stop using the system and replace the drive and/or motor; return the drive for investigation.

95.0 / 95.01: Motor Non-conformity

What it means: The connected motor does not match the drive (G5 uses sub numbers 0 to 4).^[1][2][3]

Also on: 1S shows Er 95 01.

Drive response: servo off; cannot be reset, cycle the power (1S: or Unit Restart 2400 hex); G5 does not store it in the alarm history

Likely causes

• Wrong motor model or capacity for the drive
• Encoder cable connected to the wrong motor

First checks, in this order

1. Compare the drive and motor nameplates and use a matching combination.
2. Check the encoder cable belongs to the motor wired to this drive.
3. Sysmac Studio event code: 246D0000 hex (1S), 24680000 to 246C0000 hex (R88D-KN-ECT).

95.05: Motor Replacement Detected

What it means: The motor now connected is not the one that was connected last time; this appears after replacing the motor or the drive.^[3]

Drive response: servo off; clear it in Sysmac Studio, then Unit Restart or a control power cycle

Likely causes

• Motor replaced
• Servo drive replaced

First checks, in this order

1. In Sysmac Studio go online, right-click the drive, open Motor and Encoder and click Reset Motor Replacement Detection error.
2. Run Unit Restart or cycle the control power.
3. With an absolute encoder, run the Absolute Encoder Setup and redo the origin.
4. Sysmac Studio event code: 387C0000 hex.

36.0 / 36.00: Object Error (R88D-KN-ECT) / Parameter error (R88D-KT) / Non-volatile Memory Data Error (1S)

What it means: Saved parameter data was found corrupted when it was read at power on (G5 uses sub numbers 0 to 2).^[1][2][3]

Also on: 1S shows Er 36 00.

Drive response: servo off; cannot be reset, cycle the power (1S: or Unit Restart 2400 hex); G5 does not store it in the alarm history

Likely causes

• Power cut or noise while parameters were being saved
• 1S: power cut while motor identity data or safety parameters were saved
• Drive memory fault if it keeps coming back

First checks, in this order

1. G5: reset all parameters (objects) and load them again from your backup.
2. 1S: set the parameters again, save and cycle the power; run Motor Setup if motor data was hit; for safety data clear the FSoE slave address and run FSoE Enable Reset.
3. If it repeats, replace the drive and send it for repair.
4. Sysmac Studio event code: 183A0000 hex (1S), 14A80000 to 14AA0000 hex (R88D-KN-ECT).

37.0 / 37.00: Object Corrupted (R88D-KN-ECT) / Parameters destruction (R88D-KT) / Non-volatile Memory Hardware Error (1S)

What it means: The parameter memory (EEPROM) failed its check: a memory hardware problem.^[1][2][3]

Also on: G5 uses sub numbers 0 to 2. 1S shows Er 37 00.

Drive response: servo off; cannot be reset, cycle the power (1S: or Unit Restart 2400 hex); G5 does not store it in the alarm history

Likely causes

• Faulty EEPROM in the drive
• 1S: false detection from heavy noise

First checks, in this order

1. Cycle the power.
2. If it comes back, replace the drive and return it for repair.
3. Sysmac Studio event code: 084D0000 hex (1S), 14AB0000 to 14AD0000 hex (R88D-KN-ECT).

41.0 / 41.00: Absolute Encoder Counter Overflow Error

What it means: The absolute encoder multi-turn counter went past its limit.^[1][2][3]

Also on: 1S shows Er 41 00 and gives an earlier AB.00 counter overflow warning (4510-02 hex).

Drive response: servo off; cannot be reset, cycle the power (1S: or Unit Restart 2400 hex)

Likely causes

• Wrong absolute encoder operation setting for the axis type
• Axis travelled too many turns from the origin (G5: more than 32,767 revolutions)

First checks, in this order

1. Set the absolute encoder operation selection correctly: Pn015 (R88D-KT), 3015 hex (R88D-KN-ECT), 4510-01 hex (1S).
2. Keep the travel from the origin within the encoder range.
3. Sysmac Studio event code: 38870000 hex (1S), 384E0000 hex (R88D-KN-ECT).

42.0: Absolute Encoder Overspeed Error

What it means: While running on battery only (power off), the motor turned faster than the encoder can track.^[1][2]

Also on: R88D-KT and R88D-KN-ECT.

Drive response: servo off; can be reset only after the absolute encoder is cleared

Likely causes

• Shaft turned by the load or gravity while the drive was off
• Encoder supply or CN2 connection problem

First checks, in this order

1. Check the encoder supply (5 VDC +/-5%) and the CN2 connector.
2. Stop the shaft from moving while power is off (brake, mechanical lock).
3. Clear the absolute encoder, then reset and home again.
4. Sysmac Studio event code: 18200000 hex (R88D-KN-ECT).

43.0: Encoder Initialization Error

What it means: The encoder failed its initialization at power on.^[1][2]

Also on: R88D-KT and R88D-KN-ECT.

Drive response: servo off; cannot be reset, cycle the power

Likely causes

• Noise on the encoder line
• Encoder failure

First checks, in this order

1. Improve noise measures (cable routing, shield, ground).
2. If it continues, replace the motor.
3. Sysmac Studio event code: 18210000 hex (R88D-KN-ECT).

44.0 / 44.00: Absolute Encoder 1-rotation Counter Error (G5) / 1-rotation Counter Error (1S)

What it means: The encoder found an error in its single-turn position counter.^[1][2][3]

Also on: 1S shows Er 44 00.

Drive response: servo off; cannot be reset, cycle the power (1S: or Unit Restart 2400 hex)

Likely causes

• Electrical noise
• Vibration, impact, condensation or dirt at the motor (1S)
• Encoder failure

First checks, in this order

1. Improve noise measures on the encoder cable.
2. Check the motor environment for vibration, shock, moisture and contamination.
3. If it continues, replace the motor.
4. Sysmac Studio event code: 08430000 hex (1S), 18220000 hex (R88D-KN-ECT).

45.0 / 45.00: Absolute Encoder Multi-rotation Counter Error

What it means: The encoder found an error in its multi-turn counter (R88D-KT: or in the phase A/B signals).^[1][2][3]

Also on: 1S shows Er 45 00.

Drive response: servo off; cannot be reset, cycle the power (1S: or Unit Restart 2400 hex)

Likely causes

• Electrical noise
• Temporary fault from vibration, impact or condensation (1S)
• Encoder failure

First checks, in this order

1. Improve noise measures and the motor environment.
2. 1S: if it does not return after that, keep running; if it does, replace the motor.
3. Sysmac Studio event code: 18230000 hex (1S and R88D-KN-ECT).

45.01: Absolute Position Detection Error

What it means: The encoder's multi-turn detection section reported a detection error, so the absolute position cannot be trusted.^[3]

Drive response: servo off; cycle the power or run Unit Restart (2400 hex)

Likely causes

• Detection error in the encoder multi-turn section
• Heavy electrical noise

First checks, in this order

1. Cycle the power, run the Absolute Encoder Setup and update the multi-turn data, then home again.
2. Improve noise measures; replace the motor if it repeats.
3. Sysmac Studio event code: 08460000 hex.

47.0: Absolute Encoder Status Error

What it means: The encoder was turning faster than allowed at the moment the power came on.^[1][2]

Also on: R88D-KT and R88D-KN-ECT.

Drive response: servo off; cannot be reset, cycle the power

Likely causes

• Motor moving at power on (coasting load, gravity, manual turning)

First checks, in this order

1. Make sure the motor is still when you switch the power on.
2. Sysmac Studio event code: 78020000 hex (R88D-KN-ECT).

47.00: Overspeed Error

What it means: The encoder itself detected overspeed, usually because something outside drove the motor.^[3]

Drive response: servo off; cycle the power or run Unit Restart (2400 hex)

Likely causes

• Motor turned by an external force
• Encoder failure or false detection

First checks, in this order

1. Stop external forces from spinning the motor (falling load, belt drive back-driving).
2. If it repeats, replace the motor.
3. Sysmac Studio event code: 08440000 hex.

48.0: Encoder Phase-Z Error

What it means: A missing phase Z pulse was detected on a serial incremental encoder.^[1][2]

Also on: R88D-KT and R88D-KN-ECT.

Drive response: servo off; cannot be reset, cycle the power

Likely causes

• Noise
• Encoder failure

First checks, in this order

1. Improve noise measures.
2. If it continues, replace the motor.
3. Sysmac Studio event code: 04AF0000 hex (R88D-KN-ECT).

49.0: Encoder CS Signal Error

What it means: A logic error was found in the CS signal of a serial incremental encoder.^[1][2]

Also on: R88D-KT and R88D-KN-ECT.

Drive response: servo off; cannot be reset, cycle the power

Likely causes

• Noise
• Encoder failure

First checks, in this order

1. Improve noise measures.
2. If it continues, replace the motor.
3. Sysmac Studio event code: 04B00000 hex (R88D-KN-ECT).

43.01: Encoder Memory Error

What it means: The encoder found an error in its own non-volatile memory.^[3]

Drive response: servo off; cycle the power or run Unit Restart (2400 hex)

Likely causes

• False detection from heavy noise
• Encoder memory or encoder failure

First checks, in this order

1. Cycle the power.
2. If it comes back, the encoder is faulty: replace the motor.
3. Sysmac Studio event code: 08450000 hex.

25.0: Excessive Hybrid Deviation Error (R88D-KN-ECT) / Excessive hybrid error (R88D-KT)

What it means: In fully-closed control, the load position from the external encoder and the motor position from the motor encoder drifted too far apart.^[1][2]

Also on: R88D-KT and R88D-KN-ECT, fully-closed control only.

Drive response: servo off; cannot be reset, cycle the power

Likely causes

• Coupling or belt slipping between motor and load
• External encoder wiring fault
• External feedback ratio or direction set wrong

First checks, in this order

1. Check the motor to load connection.
2. Check the external encoder and its connection to the drive.
3. Move the load and confirm the motor and external encoder counts change in the same direction.
4. Check the external feedback dividing numerator, denominator and direction (Pn324, Pn325, Pn326 or 3324, 3325, 3326 hex) and the hybrid limit (3328 hex on R88D-KN-ECT).
5. Sysmac Studio event code: 383F0000 hex (R88D-KN-ECT).

26.1: Overspeed 2

What it means: Motor speed went above the overspeed level used during an immediate stop.^[1][2]

Also on: R88D-KT and R88D-KN-ECT.

Drive response: servo off; can be reset after the cause is removed

Likely causes

• Runaway or overshoot during an immediate stop
• Immediate stop overspeed level set lower than the normal overspeed level
• Encoder wiring fault

First checks, in this order

1. Set the immediate stop overspeed level (Pn615 or 3615 hex) higher than the overspeed level (Pn513 or 3513 hex).
2. Adjust the gain if it overshoots.
3. Check the encoder wiring.
4. Sysmac Studio event code: 38400000 hex (R88D-KN-ECT).

27.0: Command pulse frequency error

What it means: The command pulse input frequency went above 1.2 times the Command Pulse Input Maximum Setting (Pn532).^[1]

Also on: R88D-KT (pulse train input) only.

Drive response: servo off; can be reset after the cause is removed

Likely causes

• Controller sending pulses faster than the drive is set for
• Pn532 set too low

First checks, in this order

1. Check the pulse frequency from the controller.
2. Check Pn532 against the real maximum pulse rate.

27.2: Command pulse multiplier error

What it means: Command pulses multiplied by the electronic gear ratio are too high, or noise is adding counts on the pulse input.^[1]

Also on: R88D-KT (pulse train input) only.

Drive response: servo off; can be reset after the cause is removed

Likely causes

• Electronic gear ratio too large
• Command pulse frequency changing sharply
• Noise on the command pulse lines

First checks, in this order

1. Keep the electronic gear ratio between 1/1000 and 1000, as low as possible.
2. Check the command pulse input and use a line driver interface if you can.
3. Set Pn532 below 1,000 to enable the digital filter.

28.0 / 28.00: Pulse regeneration error (R88D-KT) / Pulse Output Overspeed Error (1S)

What it means: The encoder pulse output (dividing output) needed a higher frequency than it can produce.^[1][3]

Also on: G5: R88D-KT only. 1S shows Er 28 00.

Drive response: servo off; can be reset after the cause is removed

Likely causes

• Encoder dividing ratio too high for the actual speed

First checks, in this order

1. R88D-KT: check the Encoder Dividing Numerator (Pn011) and Denominator (Pn503); Pn533 set to 0 disables this check.
2. 1S: correct the Encoder Dividing Pulse Output dividing numerator and denominator.
3. Sysmac Studio event code: 78200000 hex (1S).

27.1 / 27.01: Absolute Value Cleared

What it means: The absolute encoder multi-turn counter was cleared (on G5 by CX-Drive over USB). Omron says this stop is a safety measure, not a fault.^[2][3]

Also on: G5: R88D-KN-ECT only (it also has 27.7 Position Data Initialized). 1S shows Er 27 01.

Drive response: servo off; cannot be reset, cycle the power (1S: or Unit Restart 2400 hex)

Likely causes

• Absolute encoder clear performed from the software tool

First checks, in this order

1. Confirm the clear was intended.
2. Cycle the power and home the axis again.
3. Sysmac Studio event code: 98200000 hex (1S), 98010000 hex (R88D-KN-ECT).

29.0: Error counter overflow

What it means: The position error counted in encoder pulses went past 2^29 (536,870,912).^[1][2]

Also on: R88D-KT. R88D-KN-ECT splits it into 29.1 Error Counter Overflow 1 and 29.2 Error Counter Overflow 2, which cannot be reset.

Drive response: servo off; R88D-KT: can be reset after the cause is removed

Likely causes

• Motor not following the command (stalled, jammed or torque saturated)
• Torque limits too low
• Encoder wiring fault

First checks, in this order

1. Check the motor follows the position command and the torque monitor is not saturated.
2. Adjust the gain.
3. Set No. 1 and No. 2 Torque Limit (Pn013, Pn522) to maximum.
4. Check the encoder cable.

29.03: Following Error Counter Overflow

What it means: The following error value went outside the 32-bit range (-2,147,483,648 to 2,147,483,647).^[3]

Drive response: servo off; cycle the power or run Unit Restart (2400 hex)

Likely causes

• Motor not following the command
• Motor held or turned by an external force

First checks, in this order

1. Find and remove what is stopping the motor from moving.
2. Lengthen the acceleration and deceleration times.
3. Check gain and limit settings.
4. Sysmac Studio event code: 38860000 hex.

33.0 / 33.00: Interface Input Duplicate Allocation Error 1 (G5) / General Input Allocation Duplicate Error (1S)

What it means: The same function is assigned to more than one input.^[1][2][3]

Also on: G5 uses 33.1 to 33.8 for the other input group, undefined function numbers and allocation errors; 1S uses 33.09 for General Output Allocation Duplicate Error.

Drive response: servo off; cannot be reset, cycle the power (1S: or Unit Restart 2400 hex)

Likely causes

• Input function allocation parameters set twice for one function

First checks, in this order

1. Review the input allocation settings and give each function one input.
2. Cycle the power after correcting.
3. Sysmac Studio event code: 38780000 hex (1S), 38450000 hex (R88D-KN-ECT).

34.0: Overrun Limit Error

What it means: The motor moved past the allowed range set in Overrun Limit Setting relative to the position command.^[1][2]

Also on: R88D-KT and R88D-KN-ECT.

Drive response: servo off; can be reset after the cause is removed

Likely causes

• Gain unbalanced (position loop vs speed loop) or wrong inertia ratio
• Overrun limit set too small

First checks, in this order

1. Check the gain balance and the inertia ratio.
2. Increase Pn514 (R88D-KT) or 3514 hex (R88D-KN-ECT), or set it to 0 to disable the check.
3. Sysmac Studio event code: 384C0000 hex (R88D-KN-ECT).

34.01: Software Limit Exceeded

What it means: The actual position went past the software position limit and the drive stopped as set.^[3]

Drive response: servo off; can be reset after the cause is removed

Likely causes

• Software Position Limit set wrong
• Command outside the allowed range

First checks, in this order

1. Correct the Software Position Limit (3B11 hex).
2. Keep commands inside the software limit range.
3. Sysmac Studio event code: 68230000 hex.

38.01: Drive Prohibition Detected

What it means: The motor ran in a prohibited (overtravel) direction while drive prohibition was enabled, so the drive stopped it as set.^[3]

Drive response: servo off; can be reset after the cause is removed

Likely causes

• Control signal supply (12 to 24 VDC) rising slowly, giving a false trip
• Broken or wrong POT or NOT wiring
• Drive prohibition input port set wrong

First checks, in this order

1. Check how fast the control signal supply comes up at power on.
2. Check the POT and NOT wiring.
3. Check the drive prohibition settings (3B10 hex) match the actual wiring.
4. Sysmac Studio event code: 68200000 hex.

18.1 / 18.01: Regeneration Tr Error (G5) / Regeneration Circuit Error (1S)

What it means: The braking (regeneration) transistor or circuit in the drive is faulty.^[1][2][3]

Also on: 1S shows Er 18 01 (unit version 1.3 or later).

Drive response: servo off; cannot be reset, cycle the power (1S: or Unit Restart 2400 hex)

Likely causes

• Regeneration circuit failure in the drive
• 1S: short circuit between B2 and N2/N3
• 1S: noise on the external regeneration resistor wiring

First checks, in this order

1. 1S: check the regeneration resistor wiring against the connection examples and shorten it.
2. Otherwise replace the drive.
3. Sysmac Studio event code: 04B60000 hex (1S), 04AE0000 hex (R88D-KN-ECT).

18.02: Regeneration Processing Error

What it means: Regeneration processing ran for 500 ms or more, so the drive stopped it to protect the resistor.^[3]

Drive response: servo off; cycle the power or run Unit Restart (2400 hex)

Likely causes

• Regeneration settings not matched to the resistor fitted

First checks, in this order

1. Set the regeneration parameters (4310 hex) to the resistance of the resistor in use.
2. Sysmac Studio event code: 083F0000 hex.

14.02: Regeneration Circuit Error Detected during Power ON

What it means: A regeneration circuit fault was found at power on (unit version 1.2 only).^[3]

Drive response: servo off; cycle the power or run Unit Restart (2400 hex)

Likely causes

• Supply voltage low or rising slowly at power on, or fluctuating
• L1, L2, L3 not connected
• N1 and N2 terminals open
• Drive failure

First checks, in this order

1. Switch off the main power and watch the charge lamp.
2. With the lamp off, remove the wiring and check the drive and its wiring; check the external resistor value.
3. Once P to N1 reads below 1 V, measure P to N1: below 10 kohm means replace the drive. Measure B2 to N1: below 100 kohm means replace the drive.
4. Make sure the supply does not dip and rises in 500 ms or less.
5. Sysmac Studio event code: 04B30000 hex.

15.01: Motor Overheat Error

What it means: The encoder measured a motor temperature above its protection level.^[3]

Drive response: servo off; can be reset after the motor cools

Likely causes

• High temperature around the motor
• Motor overloaded
• Encoder failure

First checks, in this order

1. Bring the temperature around the motor into its operating range.
2. Lower the motor load ratio (longer cycles, lighter load).
3. Replace the motor if it repeats.
4. Sysmac Studio event code: 08420000 hex.

20.00: Runaway Detected

What it means: The motor turned in the direction opposite to the command (unit version 1.1 or later).^[3]

Drive response: servo off; cycle the power or run Unit Restart (2400 hex)

Likely causes

• Motor cable wired wrong or broken
• Motor cable and encoder cable from different motors
• Motor pushed the other way by an external force

First checks, in this order

1. Check the motor cable against the wiring diagram.
2. Make sure the motor and encoder cables belong to the same motor.
3. Remove external forces; set Runaway Detection Enable (3B71-01 hex) to 0 only if this motion is intended.
4. Sysmac Studio event code: 280D0000 hex.

35.01: System Error

What it means: Self-diagnosis found a hardware error or a fatal software error.^[3]

Also on: Related 1S codes: 35.00 FPGA WDT Error and 35.02 Self-diagnosis Error (safety function), handled the same way.

Drive response: servo off; cycle the power or run Unit Restart (2400 hex)

Likely causes

• False detection from a data read error caused by heavy noise
• Fatal software error
• Hardware failure

First checks, in this order

1. Cycle the power; if it does not return, keep running (temporary read error).
2. If it returns, replace the drive.
3. Sysmac Studio event code: 18380000 hex.

59.00: Fan Error

What it means: The cooling fan is running at 40% or less of rated speed.^[3]

Drive response: servo off; can be reset after the cause is removed

Likely causes

• Foreign matter blocking the fan
• Fan failure

First checks, in this order

1. Look for and remove anything blocking the fan.
2. If that does not fix it, replace the drive.
3. Sysmac Studio event code: 083D0000 hex.

83.1 / 83.01: EtherCAT State Change Error

What it means: The master sent a state change command that the drive cannot accept in its current EtherCAT state.^[2][3]

Also on: G5: R88D-KN-ECT only. 83.2 / 83.02 EtherCAT Illegal State Change Error is the same idea for an undefined command.

Drive response: servo off; can be reset (G5: after the cause is cleared at the master)

Likely causes

• Host controller sending state changes out of order

First checks, in this order

1. Check the host controller's state change commands against the drive specs.
2. Sysmac Studio event code: 84B10000 hex (1S and R88D-KN-ECT).

83.3 / 83.03: Communications Synchronization Error

What it means: Too many consecutive receive errors in the EtherCAT sync cycle (limit set in Communications Error Setting, 2200 hex).^[2][3]

Also on: G5: R88D-KN-ECT only.

Drive response: servo off; can be reset (G5: reset from the controller side, not from CX-Drive over USB)

Likely causes

• EtherCAT cable loose, broken or with poor contact
• Noise on the EtherCAT cable
• Master not finishing communication before the SYNC0 interrupt (G5)
• Host controller powered off during PDO communication (1S)
• Ring topology break (1S)

First checks, in this order

1. Reseat or replace the EtherCAT cables.
2. Check cable routing for noise.
3. Check the master cycle time and task load.
4. 1S in a ring: set Communications Error Setting (2200 hex) to 2 or more.
5. Sysmac Studio event code: 88100000 hex (1S), 84B30000 hex (R88D-KN-ECT).

83.4 / 83.04: Synchronization Error

What it means: The drive could not detect the signal for synchronous communication.^[2][3]

Also on: G5: R88D-KN-ECT only.

Drive response: servo off; can be reset (G5: after the cause is cleared at the master; 1S unit version 1.0: cycle the power)

Likely causes

• Control board fault (G5)
• Noise or an EtherCAT slave controller fault (1S)

First checks, in this order

1. Take noise measures on the EtherCAT cable.
2. If it returns after a power cycle, replace the drive.
3. Sysmac Studio event code: 84B40000 hex (1S and R88D-KN-ECT).

83.5 / 83.05: Sync Manager WDT Error

What it means: Process data (PDO) communication stopped for longer than allowed.^[2][3]

Also on: G5: R88D-KN-ECT only.

Drive response: servo off; can be reset (G5: after the cause is cleared at the master)

Likely causes

• EtherCAT cable disconnected, loose or broken
• Host controller stopped or faulted

First checks, in this order

1. Check the EtherCAT cables and connectors.
2. Check the host controller is running normally.
3. Sysmac Studio event code: 84B50000 hex (1S and R88D-KN-ECT).

88.1 / 88.01: ESC Initialization Error

What it means: The EtherCAT slave controller in the drive failed to initialize at power on.^[2][3]

Also on: G5: R88D-KN-ECT only.

Drive response: servo off; cannot be reset, cycle the power (1S: or Unit Restart 2400 hex)

Likely causes

• Control board or EtherCAT slave controller fault
• Data overwritten in the slave controller memory (1S)

First checks, in this order

1. Cycle the power.
2. If it comes back, replace the drive.
3. Sysmac Studio event code: 84B60000 hex (1S and R88D-KN-ECT).

88.02: Synchronization Interruption Error

What it means: The synchronization interrupt did not arrive within the specified time.^[3]

Also on: G5 R88D-KN-ECT shows 88.2 for this event code (named Interruptions Error in its error list).

Drive response: servo off; cycle the power or run Unit Restart (2400 hex)

Likely causes

• Host controller EtherCAT synchronization settings wrong

First checks, in this order

1. Set the master's synchronization settings to match the drive's EtherCAT specs.
2. Sysmac Studio event code: 84B90000 hex.

90.0: Communications Setting Error

What it means: The host sent an out-of-range EtherCAT setting or asked for an unsupported state.^[2]

Also on: R88D-KN-ECT only. On 1S, 90.00 to 90.09 are separate mailbox, PDO and DC setting errors.

Drive response: servo off; can be reset after the cause is cleared at the master

Likely causes

• Synchronous cycle (SYNC0) set to a value the drive does not support
• Unsupported state change command

First checks, in this order

1. Correct the EtherCAT settings at the master, especially the SYNC0 cycle.
2. Check the master's state change commands.
3. Sysmac Studio event code: 84B80000 hex (R88D-KN-ECT).

91.1 / 91.01: Command Error

What it means: The master gave a command the drive cannot run in its current state.^[2][3]

Also on: G5: R88D-KN-ECT only.

Drive response: servo off; can be reset after the cause is removed

Likely causes

• State change out of Operational while the servo is on with the remote bit set
• Unsupported Modes of operation (6060 hex) value
• G5: mode switched in less than 2 ms or an unsupported homing method
• 1S: pp, pv or hm mode with a communication period shorter than 250 microseconds

First checks, in this order

1. Check the host controller's commands and mode settings against the drive specs.
2. Sysmac Studio event code: 78230000 hex (1S), 74810000 hex (R88D-KN-ECT).

92.0: Encoder Data Restoration Error

What it means: In absolute mode (semi-closed control) the drive could not restore its internal position data from the encoder.^[2]

Also on: R88D-KN-ECT only.

Drive response: servo off; cannot be reset, cycle the power

Likely causes

• Encoder supply voltage low on a long cable
• Noise on the encoder cable

First checks, in this order

1. Check the encoder supply (5 VDC +/-5%).
2. Separate the encoder cable from the motor cable and connect the shield to FG.
3. Sysmac Studio event code: 08170000 hex (R88D-KN-ECT).

93.0 / 93.00: Object Setting Error 1 (G5) / Electronic Gear Setting Error (1S)

What it means: The electronic gear ratio is outside the allowed range.^[2][3]

Also on: G5: R88D-KN-ECT only (R88D-KT reports gear problems as 27.2). 1S shows Er 93 00.

Drive response: servo off; cannot be reset, cycle the power (1S: or Unit Restart 2400 hex)

Likely causes

• Gear ratio set outside 1/1000 to 1000 (G5) or 1/2,000 to 2,000 (1S)

First checks, in this order

1. Correct the electronic gear ratio objects and cycle the power.
2. Sysmac Studio event code: 387F0000 hex (1S), 384F0000 hex (R88D-KN-ECT).

94.00: Function Setting Error

What it means: A function is set that the 125 microsecond communication period does not support.^[3]

Also on: G5 R88D-KN-ECT reports a similar Function Setting Error as 93.4.

Drive response: servo off; can be reset after the cause is removed

Likely causes

• Electronic gear ratio not 1:1 at a 125 microsecond period
• Backlash compensation enabled at a 125 microsecond period

First checks, in this order

1. Set the gear ratio to 1:1 or use a longer communication period.
2. Disable backlash compensation or use a longer communication period.
3. Sysmac Studio event code: 38570000 hex.

97.00: Brake Interlock Error

What it means: At servo off the motor did not slow below the threshold speed in time, so the brake interlock output (BKIR) was forced on by the timeout.^[3]

Drive response: servo off; can be reset after the cause is removed

Likely causes

• Servo turned off while the motor was still turning fast
• Timeout at Servo OFF set too short for the machine

First checks, in this order

1. Increase Timeout at Servo OFF (4610-02 hex) to suit the real stopping time.
2. Check the sequence so servo off comes after the axis has stopped.
3. Sysmac Studio event code: 78210000 hex.

99.99: Misalignment Alert

What it means: The absolute position of the encoder may have shifted; Omron treats the encoder as faulty.^[3]

Drive response: servo off; a normal reset works only after Reset Communications Error Count

Likely causes

• Encoder failure

First checks, in this order

1. Plan a motor replacement.
2. To reset: in Sysmac Studio open Motor and Encoder, Encoder Properties, click Reset Communications Error Count, then do a normal error reset.
3. Check the machine position and home again before running.
4. Sysmac Studio event code: 18400000 hex.

39.0: Excessive analog input 1

What it means: Analog input 1 (speed or torque command) got a voltage above the Excessive Analog Input 1 setting (Pn424).^[1]

Also on: R88D-KT only; 39.1 and 39.2 are the same check for analog inputs 2 and 3 (Pn427, Pn430).

Drive response: servo off; can be reset after the cause is removed

Likely causes

• Command voltage from the controller too high
• Pn424 set too low
• Wiring fault on CN1

First checks, in this order

1. Set Pn424 correctly and check the CN1 connections.
2. Set Pn424 to 0 to disable this check if it is not needed.

50.0: External Encoder Connection Error

What it means: In fully-closed control, communication with the external encoder was lost too many times.^[1][2]

Also on: R88D-KT and R88D-KN-ECT, fully-closed control only.

Drive response: servo off; cannot be reset, cycle the power

Likely causes

• External encoder cable or connector fault
• Wrong pin connections

First checks, in this order

1. Wire the external encoder as shown in the connection diagram and fix the pin connections.
2. Sysmac Studio event code: 080C0000 hex (R88D-KN-ECT).

A0 / A0.00: Overload Warning

What it means: Early warning before 16.0: the load ratio reached 85% of the overload trip level (G5) or the Overload Warning Notification Level (1S).^[1][2][3]

Also on: 1S shows warning A0 00.

Drive response: warning; the drive keeps running; clears by itself unless warning hold is set

Likely causes

• Load or duty cycle close to the motor or drive limit
• Poor tuning or mechanical friction

First checks, in this order

1. Treat it like 16.0: check load, accel/decel times, gain and brake release.
2. 1S warning level: 4150-01 hex.
3. Sysmac Studio event code: 387A0000 hex (1S), 383C0000 hex (R88D-KN-ECT).

A1 / A1.00: Excessive Regeneration Warning (G5) / Regeneration Overload Warning (1S)

What it means: Early warning before 18.0: the regeneration load ratio reached 85% of the trip level.^[1][2][3]

Also on: 1S shows warning A1 00.

Drive response: warning; the drive keeps running

Likely causes

• Hard or frequent braking of a large inertia
• Regeneration resistor too small or set up wrong

First checks, in this order

1. Treat it like 18.0: longer deceleration, lower speed or a larger external resistor.
2. 1S: set the regeneration parameters (4310 hex) to the resistor fitted.
3. Sysmac Studio event code: 387D0000 hex (1S), 383D0000 hex (R88D-KN-ECT).

A2: Battery Warning

What it means: The absolute encoder backup battery is at 3.2 V or less.^[1][2]

Also on: R88D-KT and R88D-KN-ECT with absolute encoders.

Drive response: warning; held until reset or power cycle

Likely causes

• Battery at end of life

First checks, in this order

1. Replace the battery soon, before it causes 40.0 at the next power off.
2. If you replace it with control power on, the warning stays held: clear it with an error reset (R88D-KN-ECT: Error Reset, 4107 hex).
3. Sysmac Studio event code: 08010000 hex (R88D-KN-ECT).

A3 / A3.00: Fan Warning (G5) / Fan Rotation Warning (1S)

What it means: Cooling fan problem: on G5 the fan stopped for 1 s; on 1S fan speed is 80% or less of rated.^[1][2][3]

Also on: 1S shows warning A3 00.

Drive response: warning; the drive keeps running

Likely causes

• Dirt or foreign matter in the fan
• Fan wearing out

First checks, in this order

1. Clean the fan inlet and remove debris.
2. Plan fan or drive replacement before it turns into an overheat or 1S 59.00 Fan Error.
3. Sysmac Studio event code: 084C0000 hex (1S), 08020000 hex (R88D-KN-ECT).

A4 / A4.00: Encoder Communications Warning

What it means: Encoder communication errors happened in a row more often than allowed (1S: twice in a row); early sign of 21.x.^[1][2][3]

Also on: 1S shows warning A4 00.

Drive response: warning; the drive keeps running

Likely causes

• Noise on the encoder cable
• Poor shield or ground
• Loose encoder connector

First checks, in this order

1. Separate the encoder and motor cables, connect the shield and motor ground to FG.
2. Reseat the encoder connector.
3. Sysmac Studio event code: 083A0000 hex (1S), 08030000 hex (R88D-KN-ECT).

A6 / A6.00: Vibration Detection Warning (G5) / Motor Vibration Warning (1S)

What it means: The drive detected vibration (1S: at or above the Vibration Detection level, 3B70-01 hex).^[1][2][3]

Also on: 1S shows warning A6 00.

Drive response: warning; the drive keeps running

Likely causes

• Gain, inertia ratio or filters set wrong
• Machine rigidity dropped from looseness or wear
• Encoder cable contact problem or low encoder supply (1S)

First checks, in this order

1. Retune gain, inertia ratio and filters.
2. Check the mechanism for loose couplings, belts or bearings.
3. Check the encoder connector and cable.
4. Sysmac Studio event code: 387E0000 hex (1S), 383E0000 hex (R88D-KN-ECT).

A7: Life Expectancy Warning

What it means: The remaining life of the drive's capacitor or fan is below the set value.^[1][2]

Also on: R88D-KT and R88D-KN-ECT.

Drive response: warning; held, the drive keeps running

Likely causes

• Drive in service for a long time or in a hot cabinet

First checks, in this order

1. Plan drive (or fan) replacement at the next stop.
2. Sysmac Studio event code: 08050000 hex (R88D-KN-ECT).

A7.01: Capacitor Lifetime Warning

What it means: The capacitor inside the drive has reached its design service life.^[3]

Also on: Other 1S lifetime warnings: A7.02 Inrush Current Prevention Relay, A7.04 Brake Interlock Output Relay, A7.05 Lifetime Information Corruption, A7.06 Encoder Lifetime.

Drive response: warning; the drive keeps running

Likely causes

• Capacitor operating time past its design life

First checks, in this order

1. Plan drive replacement.
2. Sysmac Studio event code: 081C0000 hex.

B2 / B2.00: EtherCAT Communications Warning

What it means: An EtherCAT communication error happened at least once.^[2][3]

Also on: G5: R88D-KN-ECT only. 1S shows warning B2 00.

Drive response: warning; the drive keeps running

Likely causes

• EtherCAT cable loose, broken or with poor contact
• Noise
• Master powered off before the drive (normal and harmless)

First checks, in this order

1. Check the EtherCAT cables and connectors.
2. If it only appears after the master was switched off first, switch the drive off with the master.
3. Sysmac Studio event code: 84B00000 hex (1S and R88D-KN-ECT).

B1 / B1.00: Command Warning

What it means: The drive could not run a command it received from the master.^[2][3]

Also on: G5: R88D-KN-ECT only. 1S shows warning B1 00.

Drive response: warning; the drive keeps running

Likely causes

• Switch On sent with the main circuit power off
• Enable Operation sent while the motor turns at 30 r/min or more, or before a mode of operation is set
• Move commanded toward a drive prohibition (overtravel) side after an overtravel stop
• Homing or latch started under unsupported conditions

First checks, in this order

1. Check the master's command sequence and the main power state.
2. Check overtravel inputs and software limits before commanding moves.
3. Sysmac Studio event code: 78220000 hex (1S), 74800000 hex (R88D-KN-ECT).

C0.00: STO Detected

What it means: Safe torque off is active: a safety input went off or the safety controller switched STO over EtherCAT. Omron lists it as information, and the display shows ST.^[3]

Drive response: information event; motor torque stays off while STO is active

Likely causes

• Safety input 1 or 2 cable disconnected or broken
• STO turned off through EtherCAT by the safety controller

First checks, in this order

1. Reconnect or replace the safety input 1 and 2 wiring.
2. Find out why the safety controller or safety input unit removed the signal.
3. Information Level Change Selection (4030-01 hex) can turn it into an error, shown as Er C0 00.
4. Sysmac Studio event code: 98210000 hex.