What the C191A2 alarm means

A joint exceeded its configured speed limit; the safety system initiated a stop. We fix this Universal Robots CB3 / e-Series (UR5/UR10/UR16/UR20) fault almost daily, and one round of on-site checks usually confirms what is going on.

Most common causes

  • Program speed set above the configured joint speed limit
  • High acceleration through a singularity causing a joint velocity spike
  • Speed limit reduced after a safety review without updating programs
Field note: We have tallied real cases: the first cause tops the list, so start your diagnosis there.

Step-by-step field fix

  1. Reduce joint acceleration and speed in the offending move
  2. Check the safety joint speed limit settings
  3. Avoid fast wrist flips near singularities
  4. Retest at reduced speed and increase only within the configured limit
  5. Document any safety-limit change in the cell safety file
Safety first: For Universal Robots c191a2, this alarm is the safety circuit itself: jumpering a door switch or forcing a contactor removes the protection entirely - no protective action when something happens, and no defensible account of responsibility. The self-serviceable action is Reduce joint acceleration and speed in the offending move; anything past that falls under the e-stop chain and safety circuit and needs a certified engineer.

How we diagnose safety-chain faults on site

Universal Robots c191a2 belongs to the safety chain & e-stop family. On Universal Robots c191a2 the failing stage is configurable safety functions (limits, safety IO, force and power limits; finer on e-Series) on the UR control box (CB3 / e-Series) - continuity of one series loop: e-stop buttons, door switches, light curtains, safety relays and the enabling device. We start reading Universal Robots c191a2 at the PolyScope event and alarm pages; codes carry a C prefix (C15x, C5x, C7x).

The chain involved in Universal Robots c191a2 runs: e-stop / door / curtain -> safety relay (dual channel) -> controller safety input -> motor-off and brake apply.

On Universal Robots c191a2 the field usually reports Program speed set above the configured joint speed limit, but the check that matters is not continuity: The point of a safety loop is not whether it conducts but whether both channels conduct together. The relay compares channels; if one opens tens of milliseconds early it latches as a channel fault. The commonest causes are plain: oxidised door-switch contacts raising contact resistance, or one loose terminal. We measure segment by segment - pendant e-stop, panel e-stop, external e-stop, safety door - and lock onto whichever segment reads differently on the two channels.

Field notes on this page cover Universal Robots c191a2 (Safety Violation — Joint Speed Limit Violated); written by the Henghuan repair team, updated 2026-10-01.

Not sure? Don't force it — contact an engineer

Tell us these three: alarm code, robot model, and the operating condition at the alarm. Universal Robots c191a2 Universal Robots c191a2 is a diagnosis our engineers do daily, and phone/video remote diagnosis is free.

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Related Safety Chain & E-Stop alarms

C152 — Protective Stop — Position Close to Safety Plane Limits C191A1 — Safety Violation — Joint Position Limit Violated
Same family: this code belongs to the Safety chain & e-stop alarms family - the page collects all Safety chain & e-stop-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 c191a2 alarm mean?

A joint exceeded its configured speed limit; the safety system initiated a stop. We fix this Universal Robots CB3 / e-Series (UR5/UR10/UR16/UR20) fault almost daily, and one round of on-site checks usually confirms what is going on. Universal Robots c191a2 sits in the safety chain & e-stop family; on our work orders the highest-frequency trigger for this code is "Program speed set above the configured joint speed limit".

QCan I clear a Universal Robots c191a2 alarm myself?

Whether Universal Robots c191a2 clears on its own depends on the outcome of "Reduce joint acceleration and speed in the offending move". Finish the flow with "Document any safety-limit change in the cell safety file" to confirm Universal Robots c191a2 - do not skip it. If that step is clean, the second most frequent cause on Universal Robots c191a2 is "High acceleration through a singularity causing a joint velocity spike". Two attempts and still there means stop: Universal Robots c191a2 involves the e-stop chain and safety circuit, and running Universal Robots c191a2 on can turn a repairable fault into a replacement.

QA safety-chain fault like Universal Robots c191a2 stops the line - how fast can you be here?

The commonest causes we see on Universal Robots c191a2 are "Program speed set above the configured joint speed limit, High acceleration through a singularity causing a joint velocity spike, Speed limit reduced after a safety review without updating programs", so we stock the van against those. For Universal Robots c191a2 specifically, we stock along the loop: safety relays, common door switches, e-stop buttons, light-curtain pairs and terminal blocks. For Universal Robots c191a2, a safety-chain fault stops the whole line, so we rank it top priority and pre-triage by phone: door switch, e-stop or relay. Before we roll, tell us what Universal Robots c191a2 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.

The content on Universal Robots c191a2 was written by Henghuan Robotics service engineers from hands-on repair experience. Alarm descriptions are our own reference summary and may differ by controller or software version — defer to Universal Robots documentation, or contact us to confirm. Henghuan is an independent service provider with no affiliation or endorsement by Universal Robots.