ABB Error 39423 — Drive unit error
ErrorABB 39423 (“Drive unit error”): Drive unit error: the drive unit reports an abnormal condition (overcurrent, position error, communication fault) on the indicated axis. Likely part: Drive Unit / Supervision thermique (Drive Unit / Supervision thermique).
Updated 2026-10-22 · LogrobotLM reference
What it means
Drive unit error: the drive unit reports an abnormal condition (overcurrent, position error, communication fault) on the indicated axis. The message ends with a "Supervision Code": it is this code, not the event number, that identifies the faulty component. Typically appears intermittently at cold start when the ambient temperature drops below the normal range (observed on RobotWare 5.12.2040).
What to check
- Note the Supervision Code shown at the end of the message and decode it (base 8): 64 = internal arm component, typically axes 4/5/6; 256 and 512 = external axis, positioner or rectifier.
- With code 64 at cold start, suspect a fatigued solder joint or a micro-crack on the drive board: the resistance rises when cold and disappears once the cabinet is at temperature.
- Also inspect the harness running through the arm (cracked sheaths at the flex points).
- Preheat the cabinet to confirm the thermal nature before replacing the drive unit.
- Note: The Supervision Code is the truly diagnostic information in the 394xx family; never order a part based on the 39423 number alone. See 39424 (drive unit internal error) for the same reporting mechanism.
Part to check / replace
ABB 39423 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
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 →