What the 3901 alarm means

Following error between commanded and actual position exceeded the limit; the controller stops motion to protect the mechanics. Codes 3900-3999 are minor alarms that stop the current job. This is a high-frequency ticket for our EFORT repair team, and on EC2-S controller + TSINO drives systems one inspection usually identifies the fault.

Most common causes

  • Collision or obstruction in the axis path
  • Payload above rating
  • Servo gains too soft for the duty
  • Noisy encoder feedback
Field note: The top-listed cause has the highest hit rate, so checking it first narrows things down fast.

Step-by-step field fix

  1. Clear the obstruction and inspect for damage
  2. Verify payload settings
  3. Restore default gains or re-tune the axis
  4. Check encoder cable condition
  5. Re-run at reduced speed to confirm tracking
Safety first: For EFORT 3901, this alarm family points at arm motion control: after a reset the arm can move unexpectedly, and anyone inside the working envelope is at strike and pinch risk. The self-serviceable action is Clear the obstruction and inspect for damage; anything past that falls under the arm working envelope and needs a certified engineer.

How we diagnose motion alarms on site

EFORT 3901 belongs to the motion & path family. On EFORT 3901 the failing stage is matched servo drives assigned per axis in the cabinet on the EFORT robot controller - the gap between command and execution: trajectory planning, joint limits, singularities, following error and mechanical resistance. We start reading EFORT 3901 at the pendant alarm list (four-digit codes, 1xxx / 3xxx / 4xxx segments).

The chain involved in EFORT 3901 runs: program command -> trajectory planner -> joint targets -> servo execution -> actual position feedback -> deviation compare.

First check whether EFORT 3901 only appears at one pose - A six-axis arm near wrist extension or near axis-5 zero has a Jacobian approaching singularity: tiny tool moves demand huge joint rates, and the controller either reports following error or the arm snaps through. When the report is alarms at one position and clean on another path, suspect the singular region first. The fix is not raising speed limits but routing around it: move the part, add an intermediate point, or pass the region in joint interpolation.

Field notes on this page cover EFORT 3901 (Position Deviation Over Limit (EC2-S)); written by the Henghuan repair team, updated 2026-10-01.

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Related Motion & Path alarms

3910 — Joint Speed Limit Exceeded (EC2-S)
Same family: this code belongs to the Motion & path alarms family - the page collects all Motion & path-family codes we have handled, with the common inspection order and spares.
Other brands: we also keep field-fix libraries for JAKA · AUBO · ROKAE and more — see the complete alarm code hub.

Frequently asked questions

QWhat does the EFORT 3901 alarm mean?

Following error between commanded and actual position exceeded the limit; the controller stops motion to protect the mechanics. Codes 3900-3999 are minor alarms that stop the current job. This is a high-frequency ticket for our EFORT repair team, and on EC2-S controller + TSINO drives systems one inspection usually identifies the fault. EFORT 3901 sits in the motion & path family; on our work orders the highest-frequency trigger for this code is "Collision or obstruction in the axis path".

QCan I clear a EFORT 3901 alarm myself?

Whether EFORT 3901 clears on its own depends on the outcome of "Clear the obstruction and inspect for damage". Finish the flow with "Re-run at reduced speed to confirm tracking" to confirm EFORT 3901 - do not skip it. If that step is clean, the second most frequent cause on EFORT 3901 is "Payload above rating". After clearing EFORT 3901, watch it for one shift. A second trip means stop and let an engineer arrive with the right test gear for the arm working envelope.

QFor motion alarms like EFORT 3901, can you triage remotely first?

The commonest causes we see on EFORT 3901 are "Collision or obstruction in the axis path, Payload above rating, Servo gains too soft for the duty", so we stock the van against those. For EFORT 3901 specifically, we carry mechanical and configuration items: grease, limit switches, drag-chain segments, encoder cables and the parameter sheets for common reducers. For EFORT 3901, motion alarms can often be narrowed remotely first, so an on-site visit is not always immediate. Before we roll, tell us what EFORT 3901 shows on the pendant alarm list (four-digit codes, 1xxx / 3xxx / 4xxx segments) and what the machine was doing - phone or video triage is free.

The notes on EFORT 3901 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 EFORT documentation or contact us with questions. Henghuan is an independent service provider, not affiliated with or endorsed by EFORT.