You can attempt to load the BACKUP BIOS image and then re-install the BIOS image, which will attempt to overwrite the PRIMARY image. Use the following command from the BMC shell to load the backup bios image:
BMC> system reset backup
I also recommend a cold boot as that can often times release a wedged BMC or SP that's not reading the BIOS improperly preventing the controller to boot. You can do this by powering off the system, pull out all PSU's, and the faulty controller from the chassis to drain all power for several minutes.
Don't forget to run "system power on" from the BMC after re-inserting all components. Then immediately switch to the console using "system console" from BMC, so you don't miss any boot-up error messages.
If the backup BIOS image is still reporting an ERROR state then most likely the controller is damaged. Unfortunately, the controller needs to at least boot up to the LOADER prompt to proceed with any recovery efforts. Have you tried re-seating the controller and pulling the CMOS battery for several minutes?
Pressing "CTRL+G" at the BMC prompt doesn't bring you to the LOADER prompt?
You can also run "events all" from BMC and look for any BIOS, CPU, MEMORY, POST errors to see if it might be a replaceable component like a single DIMM module.