Is there a way to check Channel Utilization in CLI in FortiGate?

Hello Steaven_K,

Yes there is, you can use the command in the fortigate:

"diagnose wireless-controller wlac -c wtp <wtp-id | name>"

Near the end of the command you will see the fields:

• oper chan , is the channel 
• oper chutil data, represents the Channel utilization, where the first value is the newer value (you will see a long string of numbers separated by " , ")

Hope this helps you, best regards.