What the 4105 alarm means

The EMERGENCY connector loop check failed — the controller cannot verify the external emergency stop circuit. This is one of the faults our repair team handles on Epson RC90 / RC700 (EPSON RC+) systems — the cause is usually identifiable within the first on-site inspection.

Most common causes

  • EMERGENCY connector not plugged or not latched
  • E-stop wiring open or shorted
  • External E-stop device failed
  • Connector pin damage
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. Check that the EMERGENCY connector is fully seated and latched
  2. Inspect the E-stop loop wiring for opens and shorts
  3. Test each external E-stop device
  4. Repair or replace the connector if pins are damaged
  5. Reboot the controller after the loop is healthy
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 Safety Chain & E-Stop alarms

4150 — Redundant Input Signal Failure of Emergency Stop
Other brands: we also keep field-fix libraries for Nachi · Omron · ESTUN and more — see the complete alarm code hub.

Frequently asked questions

QWhat does the Epson 4105 alarm mean?

The EMERGENCY connector loop check failed — the controller cannot verify the external emergency stop circuit. In field practice it belongs to the safety chain & e-stop family of faults.

QCan I clear a Epson 4105 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 Epson documentation or contact us. Henghuan is an independent service provider, not affiliated with or endorsed by Epson.