0
  • No products in the cart.
Total:€0.00
FAQ
Artboard 333

How to fix failed DIAG-CONTROL Check Sequence error

Posted at April 17, 2025 in by
8 Likes

In-case you run in to the error stated above “failed DIAG-CONTROL Check Sequence” there are things you can try to solve this issue, these fixes can vary from as simple as re-coding the modules to a different firmware so it would be supported and recognized correctly, to determining whether or not the equipment itself is damage or going through the painstaking process of updating your equipment.

Understanding the Why ?

First before we try to fix the issue we must look into what could be causing such issues in your Fortinet equipment. The reason on why this type of error can appear may vary, could be that the switch/router is running on a older version, could be that the transceivers or cables are programmed with a different coding that is unsupported in that exact device.

Compatibility

  • Ensure that the DAC cable is supported by your Fortinet device.

Damage to the cable itself

  • Check for any visible damage to the DAC cable or the SFP module.
  • Re-seat the DAC cable by removing and reinserting it firmly.
  • Try a different port to see if the issue follows the DAC or stays on the same port.

Firmware (Coding)

  • Ensure that your Fortinet device is running the latest firmware. Some versions have bug fixes related to DAC connectivity.
  • If you’re using an older firmware, check Fortinet’s release notes for known issues related to DACs.

Fortinet equipment

  • If the problem persists across different cables and firmware updates, there may be a hardware issue with the Fortinet device.
  • Contact Fortinet Support to check if there are known hardware failures for your model.

Fixing the problem

We would suggest for you to contact our support team for a clear and definitive analysis of your exact situation. As the problems can vary and in each instance of an error there are many things at play. We will gladly try to help you to crack the problem and find a solution to it. So in case you have this type of error don’t hesitate to ask, we will help !