Why controller is going in Service mode?

What are the reasons PLC’s are going into service modes?


the’re several different reasons why a service boot of the PLC is triggered.
Mostly because of following reasons:

  • Hardware supervision is enabled, and at least one configured hardware module was not found at boot / removed while running / different from project setup to what is connected to the PLC
  • Cycle Time Violation of a task class (the task class was not able to finish within the configured timeframe)
  • Other Exceptions like page faults
  • Hardware watchdog

To find out the cause for a service mode, please check the system logger of the PLC.
A desciption how to use the logger from Automation Studio can be found here:

Best regards, Alex

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Hi Sandeep,
As Alex said above, there are quite a few reasons your system may go into service mode.
Please see this post for an overview of different methods to collect the log file from your PLC.
Service Mode - What is it and how to collect diagnostics.

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As B&R, we usually recommend users to implement IEC Check Library (can be found in toolbox) into their projects to understand service mode triggers. Also it can be used for checking any memory violations, array access errors etc. Once this library is in your system, you can perform a more detailed check via the logger.

Yes! And we have a detailed description of how to use the IecCheck and AdvIecChk libraries in this post.

Hello @masalsandeep1692

It looks like you got some good suggestions from multiple users here, and it has been a couple of weeks since the last activity on this post. If the answers helped you with your question, can you help the next person with the same question by marking the solution on the information which helped you the most. If you still have open questions on this topic, can you provide an update?

Thank you!