Apple Hardware Test does not boot from USB with OCLP installed

[joaofrgomes]

Hi. I have a Mid-2012 13'' MacBook Pro [MacBookPro9,2 Mac-6F01561E16C75D06], and I can no longer boot into an external USB drive with Apple Hardware Test [made with the appropriate file available at https://download.info.apple.com/Apple_Hardware_Test/022-5879-A.dmg ].

My Mac has been running macOS 13 “Ventura” 13.2.1 (22D68) for a while now under OpenCore Legacy Patcher v. 0.6.1, and has been recently upgraded to firmware version 429.0.0.0.0. I am under the impression that this firmware “breaks” AHT, or maybe even Apple Diagnostics itself, but I can indeed access the latter by pressing D upon startup.

My EFIboot partition on the external USB, which should then load AHT, however, always fails and gives me this message after being booted through OCLP boot selector:

Error: 0x8000000000000003, Cannot Load  'EFI/Drivers/TestSupport.efi'
Status: 0x00000003
OC: Boot Failed - Unsupported
OCB: StartImage failed - Unsupported

I wonder if there's any way to patch these old Apple Hardware Test .dmgs and/or USB drives to be able to run in these Macs, or some way to enter into EFI and force the Mac to do so, without breaking OCLP.

Thank you for your attention!