What the MOTN-023 alarm means

A linear/circular move passed through a wrist singularity (J5 axis near 0 degrees), where infinite joint speed would be required. The robot stops instead. This is a fault we handle frequently on FANUC R-30iA / R-30iB / R-30iB Plus systems — in most cases we can pin down the root cause on the first site visit.

Most common causes

  • Programmed path passes through the singularity posture
  • Tool orientation forcing J5 near zero on linear moves
Field note: The first item on this list is what we hit most often on real machines — clear that one before going deeper.

Step-by-step field fix

  1. Change the motion type to joint (J) for that segment
  2. Or re-teach the point with a slightly different tool angle to keep J5 off zero
  3. Use the singularity-avoidance option judiciously if the path must stay Cartesian
Safety first: For FANUC motn-023, 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. What you can check yourself first is Change the motion type to joint (J) for that segment; the arm working envelope handling is not a DIY job.

How we diagnose motion alarms on site

FANUC motn-023 belongs to the motion & path family. On FANUC motn-023 the failing stage is alpha-i / beta-i servo amplifiers with PSM supply modules and SVM servo modules (SPM where spindles fit) on the R-30iB Plus / R-30iB Mate Plus / R-30iA - the gap between command and execution: trajectory planning, joint limits, singularities, following error and mechanical resistance. We start reading FANUC motn-023 at the iPendant ALARM screen (SRVO / MOTN / SYST / INTF prefixes) together with the amplifier's 7-segment status code.

The chain involved in FANUC motn-023 runs: program command -> trajectory planner -> joint targets -> servo execution -> actual position feedback -> deviation compare.

The clearest field clue for FANUC motn-023 is Programmed path passes through the singularity posture; the discriminator is this test: The most valuable judgement on motion alarms is separating software from mechanics. We take the fixture off and re-run the same path below 10% speed: if it is clean unloaded and slow, the problem is mechanical - over-heavy tooling, shifted centre of gravity, or a joint that already has drag; if it alarms even unloaded and slow, look at program points, frame calibration and whether the path crosses a singular region. No instruments needed, and it removes half the wrong turns.

Field notes on this page cover FANUC motn-023 (In Singularity); written by the Henghuan repair team, updated 2026-10-01.

Real Field Case

Machine: FANUC M-10iA (2014)

Symptom: An M-10iA raised MOTN-023 (singularity) near a certain point and the program stalled.

What we did: Trajectory analysis showed the path crossed the wrist singularity zone; we adjusted the poses to avoid it and enabled singularity avoidance.

Result: No more singularity alarms after the path change with essentially the same cycle time; about 2 hours including re-teaching.

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Related Motion & Path alarms

MOTN-017 — Limit Error (Group / Axis) MOTN-018 — Position Not Reachable MOTN-056 — Speed Limits Used
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: see our KUKA, ABB, Yaskawa and Universal Robots field-fix libraries — or the full 10-brand hub.

Frequently asked questions

QWhat does the FANUC motn-023 alarm mean?

A linear/circular move passed through a wrist singularity (J5 axis near 0 degrees), where infinite joint speed would be required. The robot stops instead. This is a fault we handle frequently on FANUC R-30iA / R-30iB / R-30iB Plus systems — in most cases we can pin down the root cause on the first site visit. FANUC motn-023 sits in the motion & path family; on our work orders the highest-frequency trigger for this code is "Programmed path passes through the singularity posture".

QCan I clear a FANUC motn-023 alarm myself?

Whether FANUC motn-023 clears on its own depends on the outcome of "Change the motion type to joint (J) for that segment". Finish the flow with "Use the singularity-avoidance option judiciously if the path must stay Cartesian" to confirm FANUC motn-023 - do not skip it. If that step is clean, the second most frequent cause on FANUC motn-023 is "Tool orientation forcing J5 near zero on linear moves". If FANUC motn-023 returns after two clears, or the checks point at Programmed path passes through the singularity posture, stop the cell and call a professional robot repair engineer.

QFor motion alarms like FANUC motn-023, can you triage remotely first?

The commonest causes we see on FANUC motn-023 are "Programmed path passes through the singularity posture, Tool orientation forcing J5 near zero on linear moves", so we stock the van against those. For FANUC motn-023 specifically, we carry mechanical and configuration items: grease, limit switches, drag-chain segments, encoder cables and the parameter sheets for common reducers. For FANUC motn-023, motion alarms can often be narrowed remotely first, so an on-site visit is not always immediate. Before we roll, tell us what FANUC motn-023 shows on the iPendant ALARM screen (SRVO / MOTN / SYST / INTF prefixes) together with the amplifier's 7-segment status code and what the machine was doing - phone or video triage is free.

This page on FANUC motn-023 is based on the field experience of the Henghuan Robotics repair team. Alarm explanations are our own summary for troubleshooting reference and may differ across controller and software versions — if unsure, verify against FANUC documentation or reach out to us. Henghuan is an independent service provider with no affiliation or endorsement by FANUC.