What the C153 alarm means

During motion the actual TCP position deviated from the commanded path beyond the allowed tolerance, so the controller stopped the robot. We have built up many handled cases of this Universal Robots CB3 / e-Series (UR5/UR10/UR16/UR20) alarm, and usually the first on-site inspection tells us what is wrong.

Most common causes

  • External force pushing the robot (collision, dragging, vacuum/gripper snag)
  • Payload settings wrong so the robot cannot hold the path
  • Blend radius set too large for the waypoint spacing
  • Worn joints or gearing under load
Field note: Confirm or rule out the first cause first — it is the situation we encounter most.

Step-by-step field fix

  1. Look for and remove whatever was physically obstructing the robot
  2. Check the payload mass and center-of-gravity settings
  3. Reduce blend radius or space waypoints further apart
  4. Run the path slowly to locate where deviation starts
  5. If deviation appears with no external force, inspect gearing and calibration
Safety first: For Universal Robots c153, 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. On site you may look at after confirming power-off the first step yourself: Look for and remove whatever was physically obstructing the robot. Beyond that it is the arm working envelope work - leave it to a professional.

How we diagnose motion alarms on site

Universal Robots c153 belongs to the motion & path family. On Universal Robots c153 the failing stage is joint-integrated drives (motor, drive and harmonic reducer in one joint) on the UR control box (CB3 / e-Series) - the gap between command and execution: trajectory planning, joint limits, singularities, following error and mechanical resistance. We start reading Universal Robots c153 at the PolyScope event and alarm pages; codes carry a C prefix (C15x, C5x, C7x).

The chain involved in Universal Robots c153 runs: program command -> trajectory planner -> joint targets -> servo execution -> actual position feedback -> deviation compare.

If External force pushing the robot (collision, dragging, vacuum/gripper snag) on Universal Robots c153 comes with a feeling of drag, the direction is clear: Following error that stays high on one axis only is usually rising mechanical resistance, not a weak servo. We turn the axis by hand with the brake released to feel smoothness, and listen to the reducer for once-per-revolution knocking - a single tick per turn on an RV reducer usually means internal bearing or cycloid damage. Grease that is black, dry or carries metal powder is the plainest evidence. Left alone, this graduates from a motion alarm to a scrapped reducer.

Field notes on this page cover Universal Robots c153 (Protective Stop — Position Deviates from Path); written by the Henghuan repair team, updated 2026-10-01.

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Related Motion & Path alarms

C150 — Protective Stop — Position Close to Joint Limits C154 — Protective Stop — Position in Singularity C155 — Protective Stop — Robot Cannot Maintain Position C157 — Protective Stop — Collision Detected
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 Kawasaki · Staubli · Epson and more — see the complete alarm code hub.

Frequently asked questions

QWhat does the Universal Robots c153 alarm mean?

During motion the actual TCP position deviated from the commanded path beyond the allowed tolerance, so the controller stopped the robot. We have built up many handled cases of this Universal Robots CB3 / e-Series (UR5/UR10/UR16/UR20) alarm, and usually the first on-site inspection tells us what is wrong. Universal Robots c153 sits in the motion & path family; on our work orders the highest-frequency trigger for this code is "External force pushing the robot (collision, dragging, vacuum/gripper snag)".

QCan I clear a Universal Robots c153 alarm myself?

Whether Universal Robots c153 clears on its own depends on the outcome of "Look for and remove whatever was physically obstructing the robot". Finish the flow with "If deviation appears with no external force, inspect gearing and calibration" to confirm Universal Robots c153 - do not skip it. If that step is clean, the second most frequent cause on Universal Robots c153 is "Payload settings wrong so the robot cannot hold the path". After clearing Universal Robots c153, 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 Universal Robots c153, can you triage remotely first?

The commonest causes we see on Universal Robots c153 are "External force pushing the robot (collision, dragging, vacuum/gripper snag), Payload settings wrong so the robot cannot hold the path, Blend radius set too large for the waypoint spacing", so we stock the van against those. For Universal Robots c153 specifically, we carry mechanical and configuration items: grease, limit switches, drag-chain segments, encoder cables and the parameter sheets for common reducers. For Universal Robots c153, motion alarms can often be narrowed remotely first, so an on-site visit is not always immediate. Before we roll, tell us what Universal Robots c153 shows on the PolyScope event and alarm pages; codes carry a C prefix (C15x, C5x, C7x) and what the machine was doing - phone or video triage is free.

This page on Universal Robots c153 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 Universal Robots documentation or reach out to us. Henghuan is an independent service provider with no affiliation or endorsement by Universal Robots.