Cannot update firmware on 2011 27" iMac

[tpluth]

I have a 2011 27" iMac (i7 3.4GHz, 6970M 2GB, 32GB, 500GB SSD, 6TB HDD, BCM94360CD)) that I'm trying to update and no matter what I do, it won't update the firmware. It's currently on IM121.004E.B00.

I've tried the 2019-002 security update, I've tried re-installing 10.13.2 then upgrading to 10.13.6, I've tried the standalone EFI 1.9 update and all are unsuccessful.

I've had several reboots with the long tone like it's trying, but end up with a black screen and some kind of chirping sound about once a minute then it eventually reboots without updating the firmware.

I originally had the SSD formatted APFS but I've tried it as HPFS, too. I also did a clean install on the hard drive. None of these made any difference.

Any ideas?

 

[nambuccaheadsau]

Try running Disk First Aid from Recovery first, and then the update.

 

[tpluth]

I've tried all the obvious things (First Aid, PRAM reset, SMC reset) to no avail.

It still just makes the long tone with a black screen, chirps a few times and continues without updating EFI.

I'm going to remove the 6TB drive and put in a stock 1TB iMac drive.
[doublepost=1555106327][/doublepost]Putting a real iMac 1TB hard drive back in the machine did the trick!.