What the D# (-1021) alarm means

The indicated motor has been driven hard for too long; the servo system disabled power to protect the motor and amplifier from overheating. This is one of the faults our repair team handles on Omron SmartController (ACE / Viper / Cobra) systems — the cause is usually identifiable within the first on-site inspection.

Most common causes

  • Motion speed/acceleration too high for the cycle
  • Cycle time shortened without retuning the trajectory
  • Payload increased without updating the program
  • Hot cabinet raising motor temperature
Field note: the first item on this list is what we find most often on real machines. Check it before you go deeper.

Step-by-step field fix

  1. Turn high power back on
  2. Reduce the speed and/or acceleration of the motion that was in progress
  3. Repeat the failed motion and monitor whether it completes
  4. Review the duty cycle: add waits or slow the overall cycle
  5. Check cabinet cooling if the alarm is frequent
Safety first: never bypass safety circuits or force contactors closed. If the alarm involves E-stop chains, brakes or drive power, and you are not a trained robot technician, contact a professional — wrong moves here can cost you a robot or an injury.

Still stuck? Get an engineer on the phone — right now

Tell us the alarm code, the robot model and what was happening when the alarm came up. Our engineers run these diagnostics every day, and remote diagnosis by phone or video call is free.

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Hotline: +86-20-39029800 · WhatsApp: +86-188-1886-2860

Related Drive & Power Stage alarms

24 — 24V Supply Fault A# — Amplifier Fault (Joint N) h# — High Temperature — Amplifier (Joint N) hV — High Voltage Bus Fault
Other brands: we also keep field-fix libraries for ESTUN · INOVANCE · EFORT and more — see the complete alarm code hub.

Frequently asked questions

QWhat does the Omron D# (-1021) alarm mean?

The indicated motor has been driven hard for too long; the servo system disabled power to protect the motor and amplifier from overheating. In field practice it belongs to the drive & power stage family of faults.

QCan I clear a Omron D# (-1021) alarm myself?

Sometimes. Work through the step-by-step checks on this page — the first listed cause is what we find most often in the field. If the alarm returns after two attempts, or the fault involves power, brakes or safety circuits, stop and call a qualified robot service engineer.

QHow fast can a Henghuan engineer help?

On-site response in the Pearl River Delta within 30 minutes to 3 hours, across mainland China in 1-3 business days, and worldwide within 2-5 business days. Remote diagnosis by phone/WhatsApp/video is available immediately.

Written by the Henghuan Robotics repair team from field service experience. Alarm descriptions are our own summary for troubleshooting reference and may vary by controller and software version — when in doubt, check your Omron documentation or contact us. Henghuan is an independent service provider, not affiliated with or endorsed by Omron.