What the 4100 alarm means

The RC90 controller lost communication with the motion control module; jogging and program execution stop. A 41xx-class error is controller-level, not axis-level. In our Epson service archive this alarm on RC90 / RC700 (EPSON RC+) systems shows up constantly, and the first on-site inspection almost always locates it.

Most common causes

  • Controller firmware glitch after a power event
  • Loose internal module connection
  • Noise on the internal bus
  • Failing control board
Field note: The first cause is the most common in the field — check it first, then work through the rest.

Step-by-step field fix

  1. Reboot the controller
  2. If the error returns, reseat internal module connections (service personnel only)
  3. Check noise countermeasures: grounding, cable separation
  4. Update or re-initialize the controller firmware if it has been corrupted
  5. Replace the controller/control board as the last resort
Safety first: For EPSON 4100, when communication drops, controller and external devices can disagree about state; at reconnect, external axes or tooling may act on stale commands. On site you may look at after confirming power-off the first step yourself: Reboot the controller. Beyond that it is external axes and tooling interlocks work - leave it to a professional.

How we diagnose communication alarms on site

EPSON 4100 belongs to the communication family. On EPSON 4100 the failing stage is RC700-A / RC90-B and the RC series - the data link: fieldbus, Ethernet, cabinet-to-body communication and external device interfaces. We start reading EPSON 4100 at the EPSON RC+ error list and controller front-panel indicators; codes segment as 4xxx / 5xxx / 9xxx.

The chain involved in EPSON 4100 runs: physical layer (cable / connector / shield) -> link layer (protocol / baud / node ID) -> application layer (data mapping / handshakes).

If Controller firmware glitch after a power event on EPSON 4100 is intermittent and a reboot buys a while: Intermittent drops that a reboot clears for a while are usually interference. Power cables sharing a trunk with communication cables, poor common grounding between drives and robot, or a shield landed at both ends forming a ground loop all produce exactly this. We check spacing between communication and power runs, single- versus double-ended shield landing, and the cabinet earth-bar connections. The fix is often re-routing and re-grounding - no hardware - but it needs a coordinated stop.

Field notes on this page cover EPSON 4100 (Communication Error in Motion Control Module); written by the Henghuan repair team, updated 2026-10-01.

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Related Communication alarms

4105 — Emergency Connector Connection Failure 4150 — Redundant Input Signal Failure of Emergency Stop 4152 — Relay Welding Error of Main Circuit 4154 — Regeneration Resistor Overtemperature 5040 — Motor Torque Output Failure — High Power State 5041 — Motor Torque Output Failure — Low Power State
Same family: this code belongs to the Communication alarms family - the page collects all Communication-family codes we have handled, with the common inspection order and spares.
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 4100 alarm mean?

The RC90 controller lost communication with the motion control module; jogging and program execution stop. A 41xx-class error is controller-level, not axis-level. In our Epson service archive this alarm on RC90 / RC700 (EPSON RC+) systems shows up constantly, and the first on-site inspection almost always locates it. EPSON 4100 sits in the communication family; on our work orders the highest-frequency trigger for this code is "Controller firmware glitch after a power event".

QCan I clear a EPSON 4100 alarm myself?

Whether EPSON 4100 clears on its own depends on the outcome of "Reboot the controller". Finish the flow with "Replace the controller/control board as the last resort" to confirm EPSON 4100 - do not skip it. If that step is clean, the second most frequent cause on EPSON 4100 is "Loose internal module connection". After clearing EPSON 4100, watch it for one shift. A second trip means stop and let an engineer arrive with the right test gear for external axes and tooling interlocks.

QFor communication alarms like EPSON 4100, how long does a site visit take?

The commonest causes we see on EPSON 4100 are "Controller firmware glitch after a power event, Loose internal module connection, Noise on the internal bus", so we stock the van against those. For EPSON 4100 specifically, we carry common bus cables, connectors, termination resistors and shield terminals. For EPSON 4100, communication work is about tracing the physical link segment by segment; most cases close in one visit. Before we roll, tell us what EPSON 4100 shows on the EPSON RC+ error list and controller front-panel indicators; codes segment as 4xxx / 5xxx / 9xxx and what the machine was doing - phone or video triage is free.

The notes on EPSON 4100 were summarized by the Henghuan Robotics repair team from on-site service. The alarm interpretation is our empirical summary for troubleshooting reference and may vary by controller and software version — please check Epson documentation or contact us with questions. Henghuan is an independent service provider, not affiliated with or endorsed by Epson.