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ABB Error 50021 — Axis servo control / Feedback / Mechanics fault

Error

ABB 50021 (“Axis servo control / Feedback / Mechanics fault”): Axis position error (exact wording of the French message, RobotWare 6.08 cabinet): the actual position of an axis is too far from the commanded position. Likely part: Asservissement axe / Feedback / Mécanique (Asservissement axe / Feedback / Mécanique).

Updated 2026-10-22 · LogrobotLM reference

What it means

Axis position error (exact wording of the French message, RobotWare 6.08 cabinet): the actual position of an axis is too far from the commanded position. Possible causes: brake not released, mechanical jam, transmission, measurement feedback or power chain problem.

What to check

  • First check that there is no mechanical jam and that the brake is working.
  • Check the brake supply, wiring/feedback and drive chain before concluding that the motor or the Drive has failed.
  • Note: Motion supervision with high hardware diagnostic value. In the field log: 49 occurrences in the Common category, systematically co-occurring with 50056 — the signature of an axis under strain, not of a program fault.

Part to check / replace

ABB 50021 points to the hardware below — start here before ordering.

Tap a part for every code that points to it — and verify the exact variant for your controller before ordering.

Related codes

50052Joint speed too high50055Joint load high50056Joint collision detected

Indicative field information — the robot manufacturer's manual and safety procedures always prevail. Never bypass a safety device; apply lockout/tagout (LOTO) before any physical intervention. How this reference is built →