820-00281 Wont update past Catalina

[No-Clean]

Clean board, customer states that while trying to update Mac gave him an error and Mac wont install any new OS past Catalina, we tested and the problem we can replicate here.

Installing Catalina no problem, but intalling from scratch or updating past Catalina wont work it states that it is not possible to load update.

The only other problem I can see is that the Mac wont show the model year, shows serial number but not model year.

Already tried new BIOS with clean ME and diferent bios chip, same problem.

 

[2informaticos]

Did you try full BIOS (clean ME), without changing serial number?
If you do that, Fsys checksum MUST be fixed.

 

[No-Clean]

Tried with Full BIOS (clean ME) with changing serial number and the program I use automatically fixes FSYS checksum, I have used it for a while now.

Same exact problem.

 

[2informaticos]

Why didn't check without touching serial number?
Just in case...

 

[No-Clean]

Ok new clean BIOS different serial, I now have the model year but same error when trying to update or install OS

 

[2informaticos]

That new BIOS, does have clean ME?
If you are not sure, test these:

A1707 820-00281 clean ME.bin

drive.google.com

820-00281 clean ME GTFL MLH32D.BIN

drive.google.com

Don't change anything on the files...

 

[No-Clean]

Thanks, at the end before I saw this post I left the working serial number and installed MacOS via CCC from a disk image and done, small updates work fine is just full upgrades that dont, this Mac will not update past Ventura so this should work for now.

Thanks, I will keep the BIOS files just in case.