Safety CPU Boot Failure / No Program Loaded

What does No program on the controller! mean?

The safety CPU fails to enter RUN mode after power-on, with the DIAG LED on and no boot project loaded. This often occurs if the power-off to power-on pause is less than 1.5 seconds, triggering a power dip detection that prevents the existing boot project from loading.

• Insufficient power-off duration (less than 1.5 seconds) between power cycles, preventing proper CPU initialization and project loading.
• Absence of a valid boot project stored in the safety CPU's non-volatile memory (e.g., due to failed download or memory corruption).
• Defective or improperly seated memory card (e.g., SD card) if used for boot project storage.
• Internal hardware fault in the safety CPU preventing it from booting up the operating system or loading the application.

Click steps to track your progress.

1. 1

   Power off the safety CPU completely (remove 24VDC supply) and wait for a minimum of 5 seconds before re-applying power.

2. 2

   Download the complete safety PLC project, including the boot-up parameters, to the safety CPU.

3. 3

   Verify the integrity and correct insertion of the memory card (if applicable) into the CPU's slot.

4. 4

   Check the CPU's diagnostic buffer via the PLC programming software for specific boot-related error messages.

5. 5

   If the issue persists, replace the safety CPU module with a new, programmed unit.