A1502 - unable to run diagnostics

[cruiser_]

A1502 / 820-4924-A. Unable to run diagnostics or recovery over internet.

Getting errors -1003F or -1003D shorty after inputting wifi details.

Runs Catalina & Big Sur fine. EFI updated to latest for the model (481).
I can register it with my iCloud / FMA.

Tried replacing the SSD, installing fresh OS, replacing wifi card.
Tried different 'internet routes' (APs). Tried disabling FMA.

Even stood up a custom AP where I can sniff traffic - macbook successfully looks up osrecovery.apple.com and connects on port 80 (dumping below some HTTP chatter). After these few requests it disconnects and above errors show up.

What gives? What else to try?

GET / HTTP/1.1
Host: osrecovery.apple.com
Connection: Close
User-Agent: InternetRecovery/1.0

Server: dlb/1.0.2
Date: Wed, 31 May 2023 20:42:34 GMT
Content-Type: text/plain;charset=us-ascii
Content-Length: 0
Connection: close
Set-Cookie: session=1685566054~C5D3335BDE532000037245D32A7023D201C2F9AF53492FC64C492FEBF9639226; Domain=osrecovery.apple.com; Path=/; HttpOnly
Strict-Transport-Security: max-age=31536000; includeSubDomains;
Via: 17.42.252.38

[cruiser_]

Re: A1502 - unable to run diagnostics

I've just noticed that the logic board has a different serial to that of the case.

Is it possible that serial number is stored elsewhere (say, touchpad?) and diagnostics/recovery fails because of that?

[kevingill]

Re: A1502 - unable to run diagnostics

I'm not aware of serial in the trackpad and I've changed a few over the years.
I've even changed the motherboard serial several times and it's still worked OK.

Do you have an ethernet adapter to try instead of WIFI?

[cruiser_]

Re: A1502 - unable to run diagnostics

ok thanks for the confirmation. I do not have a usb ethernet adapter. This is more of a nuisance than a real problem, I just like my merchandise to be 100%

There is a lot of flux on SPI chip, someone must have played with it.

One last lead I have is the serial#, it beings with C10 - some serial number decoders I found say it's an unknown location. Might try to replace it with C02.

I wonder if the diag/recovery code is stored in SMC or EFI. Did not find any references to osrecovery.apple.com in available EFI or SMC dumps.
Have you ever seen serials starting with C10? Maybe the code starts but then goes on to validate/lookup the internals and stops.

[cruiser_]

Re: A1502 - unable to run diagnostics

Ok I am 99% certain this is down to a borked firmware file. I dumped it via linux with flashrom...
- fsys checksum is invalid
- hardware code is different
- country code in serial is unknown (C10)

How this boots and works 'fine' is beyond my understanding

xxx:/tmp$ ./macserial -i C10PF6VQFVH3
    Country: C10 - Unknown, please report!
     Year:  P - 2015
     Week:  F - 12 (19.03.2015-25.03.2015)
     Line: 6VQ - 1418 (copy 3)
     Model: FVH3 - MacBookPro12,1
  SystemModel: MacBook Pro (Retina, 13-inch, Early 2015)
     Valid: Possibly

[kevingill]

Re: A1502 - unable to run diagnostics

Ah, that doesn't look good.
Just change the serial to the same as the base plate serial and then the pair will match up.
Probably best get a clean ROM from this forum and set the serial number in that.
Hopefully that will get it going properly.

The diagnostics are on a partition of the SSD, so you'll need an install of your favourite MACOSX.

[reformatt]

Re: A1502 - unable to run diagnostics

You need to fix the Fsys block checksum in the dump after you change the serial number. Piernov has a video on YouTube on how to do it with UEFI tool and hex editor.

Diagnostics doesn't reside on the SSD anymore, it's downloaded via Internet Recovery. Invalid serial and bad checksum would explain why its not working.

[cruiser_]

Re: A1502 - unable to run diagnostics

The board inside of this case is 820-4924-09. From the files I found for this model, all of them had FVH3 as model code.
Each and every time I changed the serial to the one on the case (it indicates FVH5 model), the board wouldn't start - and cycled.

However... when I updated the serial in the 'original' dump (which was FVH3...) the board booted, new serial was visible in OS, however the diagnostics wouldn't run UNLESS i put 4D1EDE05-38C7-4A6A-9CC6-4BCCA8B38C14:MLB/HW_MLB values in NVRAM.

Tried clearing VSS/SVS - no boot.
So I spent hours de/resoldering/programming the SPI, checked multiple files and I'm a bit stuck... some sort of validation of the serial/model is kicking me in the butt :|