Universal Robots Error Codes

C4A1: Communication issue: Lost communication with Controller

What it means: Communication was lost between the Safety Control Board and the Motherboard in the Control Box.^{[1][2][4][14][16]}

Likely causes

• Faulty or loose Ethernet cable between the Safety Control Board and the Motherboard
• A script or UR+ software overloading the communication between the Safety Control Board and the Motherboard
• Software that needs updating (UR lists a software update as the last step)

First checks, in this order

1. Check the Ethernet cable between the Safety Control Board and the Motherboard.
2. Check that no script or UR+ software is overloading the communication between the two boards.
3. Do a complete rebooting sequence.
4. Update the robot software.
5. If the issue stays, UR asks you to create a case at myUR (login needed) or contact your Universal Robots distributor.

C4A2: Communication issue: Lost communication with Safety Control Board A uP

What it means: The Motherboard lost communication with processor A (A uP, also called SafetySys1) on the Safety Control Board.^{[1][2][4][14][16]}

Also on: C4A3 Communication with Safety Control Board B uP lost (processor B, SafetySys2) has the same suggestions.

Likely causes

• Bad TCP/IP connection between the Motherboard and the Safety Control Board
• A faulty Safety Control Board (UR lists exchanging it as the last step)

First checks, in this order

1. Check the TCP/IP connection between the Motherboard and the Safety Control Board.
2. Do a complete rebooting sequence.
3. If it persists, exchange the Safety Control Board.

C4A4: Communication issue: Communication with primary Teach Pendant uP lost

What it means: The Motherboard lost communication with the primary safety processor in the Teach Pendant.^{[1][2][4][16]}

Also on: C4A5 Communication with secondary Teach Pendant uP lost has the same suggestions.

Likely causes

• Bad RS485-12V connection between the Motherboard and the Teach Pendant
• A faulty Teach Pendant (UR lists exchanging it as the last step)

First checks, in this order

1. Check the RS485-12V connection between the Motherboard and the Teach Pendant, including the Teach Pendant cable.
2. Do a complete rebooting sequence.
3. If it persists, exchange the Teach Pendant.

C4A12: Communication issue: Communication with joint 0 lost

What it means: The controller lost more than one data package from joint 0 and the communication with that joint is lost. The C4 list numbers the six joints 0 to 5.^{[1][2][4][16]}

Also on: Same explanation and suggestion: C4A13 (joint 1), C4A14 (joint 2), C4A15 (joint 3), C4A16 (joint 4), C4A17 (joint 5) and C4A18 Communication with tool lost.

Likely causes

• Communication cables not connected properly (UR's first suggested check)

First checks, in this order

1. Verify that the communication cables are connected properly.
2. Do a complete rebooting sequence.
3. If the issue stays, UR asks you to create a case at myUR (login needed) or contact your Universal Robots distributor.

C4A70: Communication issue: Lost package from joint 0

What it means: One package from joint 0 was lost. UR explains it as a serial communication problem with one or more joints.^{[1][2][4][16]}

Also on: Same text: C4A71 to C4A75 (joints 1 to 5) and C4A76 Lost package from tool.

Likely causes

• Serial communication problem with one or more joints
• Communication cables not connected properly

First checks, in this order

1. UR's suggestion applies if this happens often: verify that the communication cables are connected properly.
2. Do a complete rebooting sequence.

C4A86: Communication issue: Packet counter disagreement in packet from joint 0

What it means: A packet from joint 0 arrived with a packet counter that disagrees with the expected count.^{[1][2][4][16]}

Also on: Same suggestion: C4A87 to C4A91 (joints 1 to 5) and C4A92 Packet counter disagreement in packet from tool.

Likely causes

• Communication cables not connected properly (UR's first suggested check)

First checks, in this order

1. If it happens often, verify that the communication cables are connected properly.
2. Do a complete rebooting sequence.

C4A94: Communication issue: Packet counter disagreement in packet from processor A to B

What it means: A packet sent from processor A to processor B on the Safety Control Board (A uP and B uP, also called SafetySys1 and SafetySys2) arrived with a packet counter that disagrees with the expected count.^{[1][2][4][14][16]}

Also on: Same suggestion: C4A93 Packet counter disagreement in packet from processor A to joints, C4A95 Packet counter disagreement in packet from processor A to Teach Pendant and EUROMAP.

Likely causes

• Communication cables not connected properly (UR's first suggested check)

First checks, in this order

1. If it happens often, verify that the communication cables are connected properly.
2. Do a complete rebooting sequence.
3. If the issue stays, UR asks you to create a case at myUR (login needed) or contact your Universal Robots distributor.

C4A100: Communication issue: Communication lost due to Packet counter disagreements

What it means: Communication was lost because of packet counter disagreements.^{[1][2][4][16]}

Likely causes

• Communication cables not connected properly (UR's first suggested check)

First checks, in this order

1. Verify that the communication cables are connected properly.
2. Do a complete rebooting sequence.
3. If the issue stays, UR asks you to create a case at myUR (login needed) or contact your Universal Robots distributor.

C50A5: Robot powerup issue: Powersupply voltage too low

What it means: During robot power-up the power supply voltage was too low.^{[1][2][5][16]}

Likely causes

• Problem in the 48 V cable between the power supply and the Safety Control Board (SCB)

First checks, in this order

1. Check the 48 V cable between the power supply and the Safety Control Board.
2. If the issue stays, UR asks you to create a case at myUR (login needed) or contact your Universal Robots distributor.

C50A16: Robot powerup issue: The Teach Pendant does not respond

What it means: During power-up the Teach Pendant did not respond.^{[1][2][5][16]}

Also on: C50A17 The Euromap67 interface does not respond: same causes, check the Euromap67 cable and connections and the miscellaneous safety settings.

Likely causes

• Loose wire
• Incorrect safety configuration

First checks, in this order

1. Check the Teach Pendant cable and connections.
2. Check the settings in the miscellaneous tab in the Safety menu.

C50A100: Robot powerup issue: Cable not connected

What it means: At robot power-up the controller found the robot cable not connected.^{[1][2][5][14][16]}

Also on: On e-Series and later robots the directory lists C305A2 Robot cable not connected.

Likely causes

• Robot cable between the robot arm and the Control Box not connected, or a bad connection

First checks, in this order

1. Check the cable and the connections between the robot and the Control Box.
2. UR's CB3 service manual has a troubleshooting chart for NO CABLE displayed during power up (section 7.3.2).
3. If the issue stays, UR asks you to create a case at myUR (login needed) or contact your Universal Robots distributor.

C50A101: Robot powerup issue: Short circuit in robot detected or wrong robot connected to Control Box

What it means: At power-up the controller detected a short circuit in the robot, or the wrong robot arm is connected to the Control Box.^{[1][2][5][16]}

Also on: On e-Series and later robots the directory lists C305A3 Short circuit in Robot detected or the wrong Robot is connected to the Control Box.

Likely causes

• Short circuit in the robot cable or in the robot arm
• Wrong robot type connected to the Control Box

First checks, in this order

1. Check the robot type against the Control Box.
2. Look for a short circuit in the cable and in the robot arm.

C55A23: Safety system error: Safety relay error (minus connection)

What it means: Safety relay error on the minus connection. UR explains it as a current distributor error.^[1][2][16]

Also on: Same explanation and suggestion: C55A24 Safety relay error (plus connection), C55A33 Safety relay error (a relay is stuck), C55A34 Safety relay error (relays are not on).

Likely causes

• Current distributor error
• Cable problem between the Safety Control Board and the current distributor, or between the 48 V power supply and the current distributor

First checks, in this order

1. Check the cable from the Safety Control Board to the current distributor, and between the 48 V power supply and the current distributor.
2. Do a complete rebooting sequence.
3. If the issue stays, UR asks you to create a case at myUR (login needed) or contact your Universal Robots distributor.

C55A50: Safety system error: Voltage present at unpowered robot

What it means: Voltage is present at the robot while it should be unpowered. UR explains it as a Safety Control Board hardware fault.^[1][2][16]

Also on: Same explanation and suggestion: C55A51 Voltage will not disappear from robot, C55A52 and C55A53 5V, 3V3 or ADC error (5V too low or too high).

Likely causes

• Safety Control Board hardware fault

First checks, in this order

1. Do a complete rebooting sequence.
2. If this happens more than twice in a row, replace the Safety Control Board.

C71A0: Startup check error: Hardware is size0, wrong firmware at the joint

What it means: The startup check found size 0 joint hardware running the wrong joint firmware.^[1][2][16]

Also on: C71A1 to C71A4 give the same message and suggestion for size 1 to size 4 joint hardware.

Likely causes

• Wrong firmware in the joint

First checks, in this order

1. Update the joint firmware.

C71A8: Startup check error: Motor short circuit to ground or H-bridge problems

What it means: The joint startup check found a motor short circuit to ground or a problem in the motor H-bridge.^[1][2][16]

Also on: Same explanation and suggestion: C71A7 Unknown error result, C71A9 Motor indication signal does not work, C71A10 and C71A11 Phase 1 or Phase 2 is unconnected or not working. C71A12 (Phase 3 or multiple phases) has the same suggestion.

Likely causes

• Damaged motor wires
• Bad connection in the screw terminals
• Defective PCB in the joint

First checks, in this order

1. Check the joint for damaged or loose connections.
2. If that does not solve it, replace the joint.

C71A50: Startup check error: Current sensor test failed

What it means: The joint startup check probed the current sensor and it reported the wrong current.^[1][2][16]

Also on: C71A51 has the same text. C71A52 Current sensor test failed: the sensors reported different currents when probed, same suggestion.

Likely causes

• Damaged or loose connections in the joint
• Faulty current sensor in the joint

First checks, in this order

1. Check the joint for damaged or loose connections.
2. If that does not solve it, replace the joint.

C72A1: Power Supply Unit failure: 0 PSUs are active

What it means: No power supply unit is active: the PSU was not able to deliver 48 V.^[1][2][16]

Likely causes

• PSU not delivering 48 V
• Bad power connection between the power supply and the Safety Control Board

First checks, in this order

1. Check the power connection between the power supply and the Safety Control Board.
2. If the issue stays, UR asks you to create a case at myUR (login needed) or contact your Universal Robots distributor.

C72A2: Power Supply Unit failure: 1 PSU active, but we expect 2 (UR10)

What it means: Only one power supply unit is active where a UR10 expects two.^[1][2][16]

Also on: C72A3 2 PSUs active, but we expect 1 (UR5): a UR5 flash card in a UR10 robot, check that the flash card and robot match.

Likely causes

• A PSU not able to deliver 48 V
• A UR10 flash card fitted in a UR5 robot

First checks, in this order

1. Check the power connection between the power supply and the Safety Control Board.
2. Check that the flash card and the robot match.

C74A1: Joint encoder warning: Invalid decode: Readhead misalignment, ring damaged or external magnetic field present.

What it means: Joint encoder warning: the encoder could not decode its position reading.^[1][2][16]

Likely causes

• Readhead misalignment
• Damaged encoder ring
• External magnetic field present
• Grounding or shielding problem (EMC)

First checks, in this order

1. Check grounding and shielding for EMC problems.

C75A1: Joint encoder error: Invalid decode: Readhead misalignment, ring damaged or external magnetic field present.

What it means: Joint encoder error: the joint encoder could not decode its position.^{[1][2][7][10][16]}

Likely causes

• Readhead misalignment
• Damaged encoder ring
• External magnetic field present
• Grounding or shielding problem (EMC)

First checks, in this order

1. Do a complete rebooting sequence.
2. Check grounding and shielding for EMC problems.
3. If this happens more than twice, replace the joint.

C75A2: Joint encoder error: Speed reading is not valid

What it means: Joint encoder error: the speed reading from the joint encoder is not valid.^{[1][2][7][16]}

Also on: C75A4 System error=malfunction or inconsistent calibration detected has the same suggestion.

Likely causes

• Joint encoder fault (UR's last step is to replace the joint)

First checks, in this order

1. Do a complete rebooting sequence.
2. If this happens more than twice, replace the joint.

C75A32: Joint encoder error: Signal lost =Misaligned readhead or damaged ring

What it means: Joint encoder error: the encoder signal is lost.^{[1][2][7][16]}

Also on: Same suggestion: C75A64 Signal low =Too far from magnetic ring, C75A128 Signal saturation =Too close to magnetic ring.

Likely causes

• Misaligned readhead
• Damaged encoder ring
• Grounding or shielding problem (EMC)

First checks, in this order

1. Do a complete rebooting sequence.
2. Check grounding and shielding for EMC problems.
3. If this happens more than twice, replace the joint.

C153A1: Position deviates from path: Detected by the Shoulder joint.

What it means: The robot could not follow its path and the deviation was detected by the shoulder joint. UR says either there was a collision or a setting was incorrect.^{[1][2][6][11][14][16]}

Also on: Same text: C153A0 (Base), C153A2 (Elbow), C153A3 (Wrist 1), C153A4 (Wrist 2), C153A5 (Wrist 3).

Robot response: Protective stop (UR's explanation refers to protective stops)

Likely causes

• Collision with an object in the path
• Incorrect payload setting
• Incorrect center of gravity setting
• Acceleration settings the robot cannot follow

First checks, in this order

1. Make sure no objects are in the path.
2. Check the payload, center of gravity and acceleration settings.
3. After a collision, remove the obstacle and make sure operators are out of the way before resuming.
4. With no collision, adjust the program to reduce the load, for example lower accelerations or correct use of blends.
5. If protective stops occur frequently, resolve the cause; never program an automatic reset of protective stops.

C157A0: Collision detected by joint: Detected by the Base joint.

What it means: Collision detected by the base joint: the robot could not follow the path, either because of a collision or an incorrect setting.^{[1][2][11][14][16]}

Also on: Same text: C157A1 (Shoulder), C157A2 (Elbow), C157A3 (Wrist 1), C157A4 (Wrist 2), C157A5 (Wrist 3).

Robot response: Protective stop (UR's explanation refers to protective stops)

Likely causes

• Collision with an object in the path
• Incorrect payload or center of gravity setting
• Acceleration settings too demanding

First checks, in this order

1. Make sure no objects are in the path.
2. Check the payload, center of gravity and acceleration settings.
3. Remove any obstacle and make sure operators are clear before resuming.
4. If protective stops occur frequently, resolve the cause.

C158A0: Collision detected by joint: Base. The user specified payload is 0kg, please make sure this is correct.

What it means: Collision detected by the base joint while the payload set by the user is 0 kg. UR warns that an incorrect payload mass or center of gravity can cause poor robot performance and protective stops.^[1][2][16]

Also on: Same text: C158A1 to C158A5 (Shoulder to Wrist 3) and C159A0 to C159A5 under C159 Position deviates from path.

Likely causes

• Payload mass left at 0 kg or set wrong
• Center of gravity set wrong

First checks, in this order

1. Make sure the payload mass and the center of gravity are correctly specified.

C163A0: More than 50 Protective Stops are detected on the same joint within 8 hours of operation. Base joint. Something is wrong in the application. Recurring protective stops should be resolved, ignoring it can void warranty.

What it means: More than 50 protective stops were detected on the base joint within 8 hours of operation. UR says frequent protective stops point to either an error in the application or a hardware failure in a joint.^{[1][2][11][14][16]}

Also on: Same text: C163A1 (Shoulder), C163A2 (Elbow), C163A3 (Wrist 1), C163A4 (Wrist 2), C163A5 (Wrist 3).

Likely causes

• Robot motions that cause collisions
• Wrong payload, center of gravity or acceleration settings
• Hardware failure in the joint

First checks, in this order

1. Check that the robot motions do not cause collisions.
2. Check the payload, center of gravity and acceleration settings.
3. If these settings are correct, the joint needs repair.
4. Do not ignore or auto-reset protective stops: UR says this is abuse of the robot that voids the warranty.

C191A14: Safety system violation: Robot is not braking in stop mode

What it means: During braking the safety system monitors whether the robot brakes as expected; this error means it did not.^[1][2][16]

Likely causes

• Wrong TCP configuration
• Wrong payload setting
• Wrong mounting setting

First checks, in this order

1. Check the TCP configuration, payload and mounting settings.

C191A15: Safety system violation: Robot is moving in stop mode

What it means: The robot moved while it was stopped by a safety violation or a safeguard stop.^[1][2][16]

Likely causes

• Robot physically pushed while safeguard stopped
• Wrong TCP configuration, payload or mounting settings

First checks, in this order

1. Check whether the robot is physically pushed while safeguard stopped.
2. Check the TCP configuration, payload and mounting settings.

C191A23: Safety system violation: Invalid setup of safety limits

What it means: The safety system found an invalid setup of the safety limits.^[1][2][16]

Also on: Same suggestion: C191A24 to C191A27 (Reduced Mode Output or Not Reduced Mode Output set or not set when it should not be).

Likely causes

• Firmware issue (UR's first step is to check or update firmware)

First checks, in this order

1. Check the firmware and update it.
2. Do a complete rebooting sequence.

C191A28: Safety system violation: Robot Emergency Stop exceeded maximum stop time

What it means: The robot emergency stop took longer than the maximum stop time. UR explains it as too high payload.^[1][2][16]

Also on: Same text: C191A29 System Emergency Stop exceeded maximum stop time, C191A30 Safeguard Stop exceeded maximum stop time.

Likely causes

• Too high payload
• Wrong TCP configuration, payload or mounting settings

First checks, in this order

1. Check that the maximum payload of the robot is not exceeded.
2. Check the TCP configuration, payload and mounting settings.

C192A2: Safety system fault: Robot emergency stop disagreement

What it means: The safety system reports a disagreement on the robot emergency stop. UR explains it as a problem with the E-stop in the Teach Pendant or in the robot E-stop circuit.^[1][2][16]

Also on: Same suggestion: C192A3 System emergency stop disagreement (system E-stop circuit problem), C192A4 Safeguard stop disagreement (safeguard circuit problem).

Likely causes

• E-stop button in the Teach Pendant
• Fault in the robot emergency stop circuit or its wiring

First checks, in this order

1. Check the safety devices and the cables and connections to them.

C192A6: Safety system fault: Joint position disagreement

What it means: The safety system found a disagreement on joint position.^[1][2][16]

Also on: Same suggestion: C192A7 Joint speed, C192A8 Joint torque, C192A9 TCP speed, C192A10 TCP position and C192A11 TCP orientation disagreement.

Likely causes

• Wrong TCP configuration, payload or mounting settings
• Safety settings not respected by the program

First checks, in this order

1. Check the TCP configuration, payload and mounting settings.
2. Check that the safety settings are respected.

C192A16: Safety system fault: Safety output failed

What it means: A safety output did not reach the correct value in the expected time.^[1][2][16]

Likely causes

• Short circuit on the I/O
• Wrong connection to the output

First checks, in this order

1. Check for a short circuit on the I/O or a wrong connection to the output.

C192A20: Safety system fault: SPI output error detected

What it means: SPI output error: the power supply for the I/O is not detected.^[1][2][16]

Likely causes

• Internal I/O power supply connection not correct
• External I/O power supply off or at the wrong voltage

First checks, in this order

1. Check that the connection to the internal power supply is correct.
2. If an external power supply is used, check that it is on and at the correct voltage.

C192A25: Safety system fault: Potential brownout detected

What it means: The safety system detected a potential brownout.^[1][2][16]

Likely causes

• Voltage drop on the Safety Control Board
• Defective Safety Control Board

First checks, in this order

1. UR gives no specific suggestion for this sub-code. If the issue stays, UR asks you to create a case at myUR (login needed) or contact your Universal Robots distributor.

C193A0: One of the nodes is in fault mode: Base Joint

What it means: The base joint node is in fault mode. UR's first suggestion is to see the previous error in the log.^{[1][2][10][14][16]}

Also on: Same suggestion: C193A1 Shoulder Joint to C193A5 Wrist 3 Joint. C193A6 Tool, C193A7 Screen 1 and C193A8 Screen 2 (safety processor 1 or 2 in the Teach Pendant): see previous error, then reboot.

Likely causes

• An earlier error on the base joint
• Joint firmware that needs updating

First checks, in this order

1. Look at the previous error in the log.
2. Update the firmware on the joint.
3. Do a complete rebooting sequence.

C194A128: One of the nodes is not booted or not present: Base not ready while brake release requested

What it means: Brake release was requested while the base joint was not ready. The joint must be at least in IDLE mode when brake release is requested.^[1][2][16]

Also on: Same text: C194A129 to C194A134 (Shoulder, Elbow, Wrist 1, Wrist 2, Wrist 3, Tool).

Likely causes

• Loose communication cable

First checks, in this order

1. Check for a loose communication cable.

C200A14: Safety Control Board hardware error: 48V input is too low

What it means: The Safety Control Board measured its 48 V input too low.^[1][2][16]

Also on: Same suggestion: C200A15 48V input is too high, C200A19 Robot voltage is too high.

Likely causes

• Fault in the 48 V power supply, current distributor, energy eater or Safety Control Board

First checks, in this order

1. Do a complete rebooting sequence.
2. Check the 48 V power supply, current distributor, energy eater and Safety Control Board for issues.

C200A16: Safety Control Board hardware error: 24V IO short circuited

What it means: The 24 V I/O supply on the Safety Control Board is short circuited: too high current.^[1][2][16]

Likely causes

• Short circuit or overload on the external I/O wiring
• Problem with an external power supply, if connected

First checks, in this order

1. Do a complete rebooting sequence.
2. Disconnect the external I/O connections and check the external power supply if one is connected.

C200A18: Safety Control Board hardware error: Robot voltage is too low

What it means: The robot voltage measured by the Safety Control Board is too low.^[1][2][16]

Likely causes

• Short circuit in the robot arm
• Fault in the 48 V power supply, current distributor, energy eater or Safety Control Board

First checks, in this order

1. Do a complete rebooting sequence.
2. Check for a short circuit in the robot arm.
3. Check the 48 V power supply, current distributor, energy eater and Safety Control Board for issues.

C201A0: Setup of Safety Control Board failed: Setup of Safety Control Board failed

What it means: Setup of the Safety Control Board failed: no data came from the Safety Control Board at initialization, or invalid safety parameters were received.^[1][2][16]

Also on: C201A1 SCB uA is not responding has the same suggestion.

Likely causes

• Ethernet cable between Motherboard and Safety Control Board not connected
• Invalid Safety Configuration

First checks, in this order

1. Do a complete rebooting sequence.
2. Check that the Ethernet cable between the Motherboard and the Safety Control Board is connected.
3. Verify that the setup of the Safety Configuration is valid.

C261A4: Temperature Sensor: Temperature is too high ({float} degrees Celsius)

What it means: A temperature sensor reports a temperature that is too high. UR says the ambient temperature is too high or the robot is overloaded.^[1][3][10]

Also on: C261A5 Temperature is too low: ambient temperature too low, make sure the robot operates within recommended limits.

Likely causes

• Ambient temperature too high
• Robot overloaded

First checks, in this order

1. Cool down the robot's environment and make sure the robot is operating within recommended limits.
2. Do a complete rebooting sequence.
3. If it is still not solved, contact your local Universal Robots service provider.

C261A21: Temperature Sensor: Safety Control Board temperature is too high: {float} Celsius

What it means: The temperature of the Safety Control Board is too high.^[1][3]

Likely causes

• High ambient temperature
• Faulty Safety Control Board

First checks, in this order

1. Reduce the ambient temperature.
2. Do a complete rebooting sequence.
3. Update the software.
4. Replace the Safety Control Board.
5. If it is still not solved, contact your local Universal Robots service provider.

C261A25: Temperature Sensor: The Robot power sensor temperature on the Power Board is too high: {float} Celsius

What it means: The temperature of the robot power sensor on the Power Board is too high.^[1][3]

Also on: C261A23 The Energy Removal power sensor temperature on the Power Board is too high has the same suggestions.

Likely causes

• Excessive decelerations in the robot program
• High ambient temperature
• Faulty Power Board

First checks, in this order

1. Reduce excessive decelerations in the robot program.
2. Reduce the ambient temperature.
3. Do a complete rebooting sequence.
4. Update the software.
5. Replace the Power Board.
6. If it is still not solved, contact your local Universal Robots service provider.

C262A17: Communication: Failed to communicate with {deviceName} Joint

What it means: A joint failed to start communicating as expected.^[1][3]

Also on: C262A18 Failed to communicate with TOOL: the tool failed to start communicating, reboot, update software, contact service.

Likely causes

• Robot cable between Control Box and robot arm not correctly connected or damaged
• Loose connections

First checks, in this order

1. Make sure the cable between the Control Box and the robot arm is correctly connected and has no damage.
2. Check for loose connections.
3. Do a complete rebooting sequence.
4. Update the software.
5. If it is still not solved, contact your local Universal Robots service provider.

C263A1: Motor Encoder: Motor Encoder is unavailable

What it means: The motor encoder is unavailable: its sense signal indicates a bad connection.^[1][3]

Likely causes

• Bad motor encoder connection

First checks, in this order

1. Do a complete rebooting sequence.
2. Update the software.
3. If it is still not solved, contact your local Universal Robots service provider.

C263A41: Motor Encoder: The rate of invalid samples is too high. Debt counter = {unsigned}

What it means: The motor encoder delivers too many invalid samples.^[1][3]

Likely causes

• Faulty motor encoder
• Bad connection
• EMC or ESD issue

First checks, in this order

1. Do a complete rebooting sequence.
2. Check for possible electromagnetic noise or ESD sources.
3. Update the software.
4. If it is still not solved, contact your local Universal Robots service provider.

C265A0: Joint Encoder: Joint encoder position invalid. Detailed error: {hex}

What it means: A critical error occurred in the joint encoder and the position it reports is not valid.^{[1][3][8][10]}

Likely causes

• Joint encoder fault
• ESD noise

First checks, in this order

1. Do a complete rebooting sequence.
2. Check for ESD noise.
3. Update the software.
4. If it is still not solved, contact your local Universal Robots service provider.

C265A5: Joint Encoder: Near operation limits. Status: {hex}

What it means: The joint encoder is close to its operational limits and the positions it reports have reduced precision.^[1][3][8]

Likely causes

• Encoder operating close to its limits
• ESD noise

First checks, in this order

1. Do a complete rebooting sequence.
2. Check for ESD noise.
3. Update the software.
4. If it is still not solved, contact your local Universal Robots service provider.

C265A6: Joint Encoder: Not present. Status: {hex}

What it means: The joint encoder is not responding to commands.^[1][3][8]

Likely causes

• Joint encoder not responding
• ESD noise

First checks, in this order

1. Do a complete rebooting sequence.
2. Check for ESD noise.
3. Update the software.
4. If it is still not solved, contact your local Universal Robots service provider.

C265A41: Joint Encoder: The read head temperature is outside the allowed range.

What it means: The joint encoder read head is too cold or too hot.^[1][3][8]

Likely causes

• Ambient temperature too high
• Robot overloaded

First checks, in this order

1. Cool down the environment.
2. Make sure the robot is operating within the recommended limits.

C265A42: Joint Encoder: Signal amplitude low.

What it means: The joint encoder signal amplitude is low: the distance between the read head and the ring is too large.^[1][3][8]

Also on: C265A43 Signal amplitude too high: the read head is too close to the ring, same suggestion.

Likely causes

• Read head too far from the encoder ring

First checks, in this order

1. Do a complete rebooting sequence.
2. Update the software.
3. If it is still not solved, contact your local Universal Robots service provider.

C265A46: Joint Encoder: Encoder acceleration too high.

What it means: The joint encoder position data changed unexpectedly (acceleration too high).^[1][3][8]

Likely causes

• Stray magnetic field present
• Metal particles between the read head and the ring

First checks, in this order

1. Remove any sources of magnetic fields external to the robot, then do a complete rebooting sequence.
2. Update the software.
3. If it is still not solved, contact your local Universal Robots service provider.

C265A47: Joint Encoder: Magnetic pattern decoding error

What it means: The joint encoder could not decode the magnetic pattern.^[1][3][8]

Likely causes

• Stray magnetic field present
• Metal particles between the read head and the ring
• Radial position of the read head to the ring out of tolerance

First checks, in this order

1. Remove any sources of magnetic fields external to the robot, then do a complete rebooting sequence.
2. Update the software.
3. If it is still not solved, contact your local Universal Robots service provider.

C265A48: Joint Encoder: Signal lost.

What it means: The joint encoder signal is lost.^[1][3][8]

Likely causes

• Read head out of alignment with the ring
• Damaged encoder ring

First checks, in this order

1. Do a complete rebooting sequence.
2. Update the software.
3. If it is still not solved, contact your local Universal Robots service provider.

C265A49: Joint Encoder: Signal amplitude too high. External magnetic field is present

What it means: The joint encoder signal amplitude is too high because an external magnetic field disturbs the position reading.^[1][3][8]

Likely causes

• External magnetic field near the joint

First checks, in this order

1. Remove any sources of magnetic fields external to the robot, then do a complete rebooting sequence.
2. Update the software.
3. If it is still not solved, contact your local Universal Robots service provider.

C265A50: Joint Encoder: System error. Malfunction inside the circuitry.

What it means: System error inside the joint encoder circuitry. UR says cycling the power supply can reset the system error bit; the supply rise time should be shorter than 20 ms.^[1][3][8]

Also on: C265A52 System error. Inconsistent calibration data is detected: same reset note and suggestion.

Likely causes

• Malfunction inside the encoder circuitry

First checks, in this order

1. Do a complete rebooting sequence.
2. Update the software.
3. If it is still not solved, contact your local Universal Robots service provider.

C274A1: Control box fan error: Fan is not running

What it means: The Control Box fan is not running. It must run to keep the Control Box from overheating.^[1][3]

Likely causes

• Fan blocked and unable to rotate
• Fan connector not attached

First checks, in this order

1. Make sure the fan in the Control Box can rotate freely and its connector is attached. The fan sits between the air filter and the energy eater in the Control Box.
2. See the Service Manual for details.

C281A3: Robot State Machine: {deviceName} joint entered the Fault State

What it means: A joint entered the Fault State.^[1][3]

Also on: Same suggestion: C281A4 joint entered the Violation State, C281A20 joint entered the Critical Fault State, C281A7 Teach Pendant entered the Fault State.

Likely causes

• A fault in the named joint

First checks, in this order

1. Do a complete rebooting sequence.
2. Update the software.
3. If it is still not solved, contact your local Universal Robots service provider.

C281A9: Robot State Machine: {deviceName} joint moved too far before robot entered RUNNING State

What it means: A joint moved more than the permissible range during the brake release procedure, before the robot reached RUNNING state.^[1][3]

Likely causes

• Mounted payload, TCP or center of gravity not matching the configuration

First checks, in this order

1. Do a complete rebooting sequence.
2. Make sure the mounted payload, TCP and center of gravity match your configuration.
3. Update the software.
4. If it is still not solved, contact your local Universal Robots service provider.

C281A17: Robot State Machine: {deviceName} joint entered the Brake Failure State

What it means: A joint brake system failed to engage while the robot was powering down.^[1][3][12]

Robot response: On UR Series robots UR's service handbook says power to the joint motors is kept on and the arm is held at standstill until an operator powers it off in a controlled way

Likely causes

• Joint brake system failed to engage

First checks, in this order

1. Keep the robot powered on and contact your local Universal Robots service provider.
2. UR Series service handbook: before powering off, make sure it cannot harm people or damage equipment beneath the robot, because the brake is likely not engaged and the joint may not hold the arm.
3. UR Series service handbook: the robot will not brake release again until the brake has been inspected.

C283A0: Safety system: Critical error

What it means: A critical error occurred in the safety system.^{[1][3][9][10]}

Likely causes

• Safety system error (no specific cause given)

First checks, in this order

1. Do a complete rebooting sequence.
2. Update the software.
3. If it is still not solved, contact your local Universal Robots service provider.

C283A7: Safety system: {deviceName} joint exceeded the speed limit of the safety settings

What it means: A joint exceeded the joint speed limit set in the safety settings.^[1][3][9]

Also on: Same suggestion: C283A43 joint moved too quickly toward a Joint position limit, C283A47 joint position limit exceeded.

Likely causes

• Mounted payload or center of gravity not matching the installation settings
• Movements too fast, including moving the robot too fast in Freedrive
• Safety settings too tight for the application

First checks, in this order

1. Make sure the mounted payload and center of gravity match your installation settings.
2. Slow down movements; in Freedrive, move the robot slower.
3. Check the safety settings.

C283A8: Safety system: The System Emergency Stop Output is not active

What it means: The safety system failed to activate the System Emergency Stop Output. The output is active when its voltage is low.^[1][3][9]

Likely causes

• Output short circuited to a power supply

First checks, in this order

1. Make sure the output is not short circuited to a power supply.

C283A10: Safety system: Robot Emergency Stop Input disagreement within the safety system

What it means: The safety system sees a disagreement between the two Robot Emergency Stop inputs: the signals are not switching at the same time or are wired incorrectly.^[1][3][9]

Also on: Same text: C283A9 System Emergency Stop Output, C283A11 System Emergency Stop Input, C283A12 Safeguard Stop Input, C283A13 Safeguard Reset Input, C283A14 Operation Mode input and C283A15 Three-Positional Enabling Device Input disagreement.

Likely causes

• Input channels not switching simultaneously
• Inputs incorrectly connected

First checks, in this order

1. Make sure both inputs are properly connected.
2. If it is still not solved, contact your local Universal Robots service provider.

C283A17: Safety system: Lost {unsigned} Teach Pendant safety packages in a row

What it means: The safety system lost several Teach Pendant safety packages in a row.^[1][3][9]

Likely causes

• Teach Pendant not properly connected

First checks, in this order

1. Check that the Teach Pendant is properly connected.
2. Do a complete rebooting sequence.
3. Update the software.
4. If it is still not solved, contact your local Universal Robots service provider.

C283A19: Safety system: Invalid gravity vector received

What it means: The safety system received a gravity vector outside the allowed range.^[1][3][9]

Likely causes

• A script command setting an invalid gravity vector

First checks, in this order

1. Make sure no script commands set an invalid gravity vector.

C283A26: Safety system: Force limitation: A joint exceeded the torque window by {float}Nm

What it means: Force limitation: a joint exceeded its torque window. UR says a very jerky target trajectory, for example sensor based control with path_offset() or servoj(), can push target joint torques past the safety limits.^[1][3][9]

Likely causes

• Jerky target trajectory
• Noisy sensors or communication jitter in external control

First checks, in this order

1. Check that the target trajectory is smooth.
2. Look for noisy sensors or communication jitter in the external control.

C283A41: Safety system: TCP Velocity violates limits of maximum stopping time

What it means: The TCP (tool) velocity violates the maximum stopping time limit in the safety settings.^[1][3][9]

Also on: Same suggestion: C283A42 TCP Velocity violates limits of maximum stopping distance, C283A51 and C283A52 (tool or elbow speed limit exceeded).

Likely causes

• Mounted payload or center of gravity not matching the installation settings
• Movements too fast, including in Freedrive
• Safety settings

First checks, in this order

1. Make sure the mounted payload and center of gravity match your installation settings.
2. Slow down movements; in Freedrive, move the robot slower.
3. Check the safety settings.

C283A191: Safety system: A payload mass above the maximum payload limit was received. Actual value is {float}kg

What it means: The safety system received a payload mass above the maximum payload limit.^[1][3][9]

Also on: C283A190 A payload mass below the minimum payload limit was received: same suggestion.

Likely causes

• A script command setting an invalid payload mass

First checks, in this order

1. Make sure no script commands set an invalid payload mass.

C284A0: Brake Release: Critical error

What it means: A critical error occurred during brake release.^[1][3]

Also on: C260A0 Critical error under C260 Brake Release - old procedure has the same suggestion.

Likely causes

• Mounted payload, TCP or center of gravity not matching the configuration

First checks, in this order

1. Do a complete rebooting sequence.
2. Make sure the mounted payload, TCP and center of gravity match your configuration.
3. If it is still not solved, contact your local Universal Robots service provider.

C284A21: Brake Release: Brake release count reached limit

What it means: The joint reached the maximum number of allowed brake releases and can no longer release its brakes.^[1][3]

Also on: C284A22 Brake release count is close to the limit: an early warning with the same suggestion.

Robot response: The joint can no longer release its brakes

Likely causes

• Brake release count limit reached

First checks, in this order

1. Update the software.
2. Contact your local Universal Robots service provider.

C296A1: Start up check: SCB IO failed to power on

What it means: At startup the Safety Control Board I/O failed to power on.^[1][3]

Likely causes

• IO Power Connector on the Safety Control Board not connected to 24 V DC

First checks, in this order

1. Make sure the IO Power Connector on the Safety Control Board is connected to the 24 V DC.

C296A2: Start up check: One or more Motor phases is short circuited to ground. Diagnostic data: {hex}

What it means: The startup check found one or more motor phases short circuited to ground (bit 0 high in the diagnostic data).^[1][3]

Likely causes

• Motor phase short circuited to ground

First checks, in this order

1. Contact your local Universal Robots service provider.

C296A4: Start up check: Phase 1 is not connected. Diagnostic data: {hex}

What it means: The startup check found motor phase 1 not connected (bit pattern 0b0110 in the diagnostic data).^[1][3]

Also on: C296A5 Phase 2 and C296A6 Phase 3 is not connected: same suggestion.

Likely causes

• Motor phase 1 not connected

First checks, in this order

1. Make sure all motor phases are connected correctly.
2. Contact your local Universal Robots service provider.

C296A44: Start up check: 24V voltage is not operating at an acceptable level, the actual value is {float}V

What it means: The 24 V supply is not within its acceptable operating range.^[1][3]

Likely causes

• 24 V power supply or its connections

First checks, in this order

1. Check the 24 V power supply and connections.
2. Contact your local Universal Robots service provider if the issue persists.

C305A1: Robot Power Control: Power supply voltage too low

What it means: The robot power control found the power supply voltage too low.^[1][3]

Also on: C305A6 Power supply voltage too high: check loose connections and the robot cable, then reboot.

Likely causes

• Loose connections

First checks, in this order

1. Check for loose connections.
2. Do a complete rebooting sequence.
3. Update the software.
4. If it is still not solved, contact your local Universal Robots service provider.

C305A2: Robot Power Control: Robot cable not connected

What it means: The robot cable is not connected.^[1][3]

Likely causes

• Cable between Control Box and robot arm not connected correctly or damaged
• Loose connections

First checks, in this order

1. Make sure the cable between the Control Box and the robot arm is correctly connected and has no damage.
2. Check for loose connections.
3. Do a complete rebooting sequence.
4. Update the software.
5. If it is still not solved, contact your local Universal Robots service provider.

C305A3: Robot Power Control: Short circuit in Robot detected or the wrong Robot is connected to the Control Box.

What it means: A short circuit was detected in the robot, or the wrong robot arm is connected to the Control Box.^[1][3]

Likely causes

• Short circuit in the robot
• Wrong robot connected to the Control Box
• Loose or damaged robot cable

First checks, in this order

1. Check for loose connections.
2. Make sure the cable between the Control Box and the robot arm is correctly connected and has no damage.
3. Do a complete rebooting sequence.
4. Update the software.
5. If it is still not solved, contact your local Universal Robots service provider.

C305A4: Robot Power Control: Robot voltage rising slower than expected

What it means: The robot voltage is rising slower than expected at power on.^[1][3]

Likely causes

• Power supply problem
• Control Box and robot arm not correctly paired

First checks, in this order

1. Verify the power supply.
2. Verify that the Control Box and the robot arm are correctly paired.
3. If it is still not solved, contact your local Universal Robots service provider.

C306A1: Joint: Not stopping fast enough

What it means: A joint was unable to come to a full stop fast enough.^[1][3]

Likely causes

• Incorrect payload mounted
• An external force pushing the robot

First checks, in this order

1. Check for an incorrect payload or an external force pushing the robot.
2. Do a complete rebooting sequence.
3. Update the software.
4. If it is still not solved, contact your local Universal Robots service provider.

C306A9: Joint: Joint moved more than allowable limit

What it means: A joint moved more than the allowable limit. UR names a potential mechanical failure of the joint brakes.^[1][3]

Likely causes

• Potential mechanical failure of the joint brakes

First checks, in this order

1. Do a complete rebooting sequence.
2. Update the software.
3. If it is still not solved, contact your local Universal Robots service provider.

C341A22: Motor encoder: Detailed status error: Signal clipping, strong external magnetic field is present.

What it means: Motor encoder signal clipping caused by a strong external magnetic field.^[1][3]

Likely causes

• Strong external magnetic field

First checks, in this order

1. Make sure the application is not exceeding the capabilities of the robot.
2. Do a complete rebooting sequence.
3. Update the software.
4. If it is still not solved, contact your local Universal Robots service provider.

C341A24: Motor encoder: Detailed status error: ASIC was reset, external RFI glitch caused encoder to reset.

What it means: The motor encoder ASIC was reset by an external RFI (radio frequency interference) glitch.^[1][3]

Also on: C341A25 ASIC synchronization lost (external RFI glitch): same suggestion.

Likely causes

• Strong RFI source near the robot

First checks, in this order

1. Try to remove any obvious sources of strong RFI.
2. Do a complete rebooting sequence.
3. Update the software.
4. If it is still not solved, contact your local Universal Robots service provider.

C350A0: Failed brake system: Joint position drifted more than allowed

What it means: While in the failed brake state, the joint position drifted more than allowed.^[1][3]

Likely causes

• Failed joint brake system

First checks, in this order

1. Contact your local Universal Robots service provider.

C350A1: Failed brake system: State transition is not permitted with a failed brake system

What it means: The joint brake system has failed, so the joint is not allowed to enter a state where it can be moved.^[1][3]

Robot response: The joint is not permitted to enter a state where it can be moved

Likely causes

• Failed joint brake system

First checks, in this order

1. Contact your local Universal Robots service provider.

C350A3: Failed brake system: Failure detected in brake system

What it means: A failure was detected in the brake system: the brake system failed to engage.^[1][3][12]

Likely causes

• Brake system failed to engage

First checks, in this order

1. UR gives no suggestion for this sub-code. The UR Series service handbook describes the brake check for a joint reported with a faulty brake: move the arm part on that joint in both directions; a correctly engaged brake allows only about 1 to 2 degrees of motion before it hits the brake pin.
2. If the arm slid down towards the ground when it was first powered off, the brake system is faulty and should be serviced.
3. Contact your local Universal Robots service provider.

C357A0: Too high static load on {deviceName}: Payload CoG is outside reach of robot

What it means: The robot cannot lift this much payload in its current position because the payload center of gravity is outside its reach.^[1][3]

Likely causes

• Payload center of gravity extended too far out horizontally from the robot base

First checks, in this order

1. Check how far the payload center of gravity sits out horizontally from the robot base; UR names that as the cause.

C357A1: Too high static load on {deviceName}: Reorientation of tool causes load on joint to be too high

What it means: Reorienting the tool puts too high a load on a joint; the robot cannot lift this payload in its current position.^[1][3]

Likely causes

• Payload center of gravity far from the joint rotation axes

First checks, in this order

1. Re-orient the wrist to move the payload center of gravity closer to the rotation axes of the joints, for example horizontally downwards.

C742A2: Control Box temperature: The temperature of {signed} °C is above the limit

What it means: The temperature inside the Control Box is above the limit.^[1][3]

Also on: C742A1 The temperature is close to the limit: same suggestions.

Likely causes

• High ambient temperature
• Poor ventilation around the Control Box

First checks, in this order

1. Reduce the ambient temperature.
2. Improve the ventilation around the Control Box.
3. If it is still not solved, contact your local Universal Robots service provider.