# UR 3 cannot initial, and found Wrist1 booting and C4A91 error

**URL:** <https://forum.universal-robots.com/t/ur-3-cannot-initial-and-found-wrist1-booting-and-c4a91-error/20843>\
**Category:** Technical Questions\
**Created:** [April 26, 2022, 7:49am UTC](https://forum.universal-robots.com/t/ur-3-cannot-initial-and-found-wrist1-booting-and-c4a91-error/20843 "2022-04-26T07:49:45Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![anon22664553](https://avatars.discourse-cdn.com/v4/letter/a/d07c76/32.png) [@anon22664553](https://forum.universal-robots.com/u/anon22664553)\
**Post date:** [April 26, 2022, 7:49am UTC](https://forum.universal-robots.com/t/ur-3-cannot-initial-and-found-wrist1-booting-and-c4a91-error/20843/1 "2022-04-26T07:49:45Z")

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When I boot up and initial UR 3, the robot stayed at initilization.  
On running program page, we found Wrist1 shows booting and C4A91 error is found.

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**Author:** ![akbari.ara](https://avatars.discourse-cdn.com/v4/letter/a/9dc877/32.png) [@akbari.ara](https://forum.universal-robots.com/u/akbari.ara)\
**Post date:** [May 20, 2026, 2:34pm UTC](https://forum.universal-robots.com/t/ur-3-cannot-initial-and-found-wrist1-booting-and-c4a91-error/20843/2 "2026-05-20T14:34:40Z")

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any solution for this?