Universal Robots CB3 Error Code C4A5: Communication with secondary Teach Pendant uP lost

Universal Robots Robot Major Communication

Model: CB3 (UR3/UR5/UR10) | Code: C4A5

Applicable Systems
UR3 UR5 UR10 UR3e UR5e UR10e UR16e UR20 UR30

Symptoms

Communication with secondary Teach Pendant uP lost

Troubleshooting Steps

  1. Step 1: Check RS485-12V connection between Motherboard and Teach Pendant,
    Check if the issue is resolved after this step
  2. Step 2: Conduct a complete rebooting sequence,
    Check if the issue is resolved after this step
  3. Step 3: Exchange Teach Pendant
    Check if the issue is resolved after this step

How to Reset

Power cycle the robot controller and perform a complete reboot sequence. If the error persists, update the software to the latest version.

Related Universal Robots Fault Codes

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Source: Universal Robots Official Error Codes Directory (https://www.universal-robots.com/manuals/EN/PDF/Shared/ErrorCodes/ErrorCodes.pdf)

Category: Robot

Published: 2026-10-23