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Amit Pandey

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Amit Pandey
Asked:15 Jan 2026

SIMATIC S7-200: Central processing unit 226 malfunction

Dear All,
I have peculiar problem with one of my CPU 226 meant for a traverse/reverse motion application.
The machine is not performing as per the set program. Instead, sometimes it completes the forward movement and does not return to the reverse movement even after the program sequence is completed.
CPU Type No:
6ES7-216-2BD23 with 32KB memory module.
Can you please give your feedback on what could have gone wrong?
Regards
Sree

#SIMATIC S7-200 #sosflex #siemens
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Answers(1)
Deleted Member Added an Answer on17 Jan 2026

Troubleshooting CPU 226 Motion Issue

Dear Sree,

Regarding your issue with the CPU 226 (6ES7-216-2BD23) failing to return during traverse/reverse motion, several factors could be at play. Here's a breakdown of potential causes and troubleshooting steps:

  • Program Logic: Carefully review your program logic, particularly the sections controlling the reverse motion. Ensure the correct conditions are met for triggering the reverse sequence.
  • Output Issues: Verify the output signals controlling the reverse motion are being activated correctly. Check wiring and the status of the output module.
  • Hardware Fault: Although less common, a fault within the CPU or output module is possible.
  • Interference: Electrical noise can sometimes cause erratic behavior. Ensure proper grounding and shielding.
  • Memory Module: While the 32KB memory is generally reliable, a rare memory issue cannot be completely ruled out.

Recommended Actions:

  1. Detailed Program Review: Step through the program in Online mode to observe the logic flow and signal states.
  2. Diagnostic Buffer: Check the CPU's diagnostic buffer for any error codes or warnings.
  3. Signal Monitoring: Monitor the input and output signals related to the motion control in real-time.
  4. SiePortal Resources: Consult the Siemens Industry Online Support for FAQs, manuals, and application examples related to S7-200 series.

If the issue persists, please provide more details about your program structure and any error messages you encounter.

Sincerely,
Siemens Self Support

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