This is a stupid question but I have a 820-00165 that boots to the OS but strangely loses the trackpad at the login

I was trying to install OS X Catalina on a repaired machine off a USB drive installer that I have used many times.
The trackpad works at this point. Its when I get to the language INSTALL screen (i.e where you pick the language to proceed with the install)
that the cursor freezes in the upper left hand corner of the screen.

I inspected the trackpad cable and it not good so I replaced it.
Same issue.
I am now US cleaning the board as the connector may have some debris in it.

My question:

Why does the trackpad work when the machine first starts (power button + option key pressed) and USB drive in place, but stop working when it gets to the language select screen on the Catalina install. I was hesitant to even post this as I though it was surely a software issue that I was dealing with such as an install issue but
I think it is a hardware issue and the trackpad connector is to blame.


Staff member
Try USB preinstalled macOS.
Does the TP stop to work when you get logged in?
If yes, check all TPAD_SPI related resistors.


Tried it with a USB connected SSD with pre-installed Mojave.
Boots all the way to the login screen and thats where the cursor freezes.

The board is cleaned now and is being dried.


OK informaticos


Machine boots into OS now WORKS FINE
Ran Apple Diagnostics

NCD001 there may be a problem with the camera

Camera works fine.

I replaced J4002 since I had nicked it when replacing a fan connector
Again, camera works fine. Boots into OS.

C4013 measured 14 UF but thats on the board so I'm not sure what that means

I don't want to return a board to the customer unless I know that the camera issue is not significant


this is stupid but with a cmi zapper should i copy the mac rom to the medusa

then reflash the bios with the copy from the medusa?


there is a cleaned ME BIOS on mac now (i just cleaned it)

next step... copy BIOS to Medusa from MAC
flash Mac with the same copied BIOS from the Medusa?

seems kind of circular?

And that can explain an NDC001 error?


Staff member
This issue caused by new OS installation has nothing to do with hardware.
So you must get back original, or other known good BIOS with clean ME.
The way you exposed doesn't help, as you didn't backup BIOS BEFORE OS installation.
Just in case, I still recommend to make a backup NOW.

You need to upload new file into Medusa and write it to Mac board; ME region MUST be cleaned after that.
If you swap original Fsys area into new file (before write in Mac board), that's all.
If not, need to fix Fsys checksum too; supposing you've changed serial number into new file.


OK I connected the Medusa to the MAC
Copied MAC ROM to Medusa
Connected the Medusa now to my TL866II
Read the Medusa ROM and saved a .BIN copy to my PC

I now have a backup copy of the FULL ROM on my PC

Now how do I get a copy of a known RELIABLE SAFE good BIOS for an 820-00165 (Google?)?

Confirm next steps:

1) Get new good BIOS
2) swap original Fsys area into new BIOS file in the TL866II software
3) NOW load the GOOD BIOS with swapped Fsys into the MEDUSA
4) Write to the MAC ROM from the Medusa

5) Clean the ME region on the MAC ROM using the Medusa

Is that correct?

By the way I am doing this slowly and carefully because this is new to me and I am learning this for the first time.

In the future I will ALWAYS back up the BIOS before an OS install.

Do you want me to upload the backup I made so you can see it?


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Staff member
The steps sequence is correct.
Just use HxD to process BIOS file, is the easiest way.

We should have few links posted on the forum for 00165 BIOS...


OK I did the following:

new BIOS from here:
That was a MBA 2015 820-00165 BIOS I think

replaced ssn
replaced hwc

Got correct new checksum and replaced old checksum

Please tell me if I did it right.


I have the OLD BIOS .BIN file backed up on my PC so I should be safe to proceed with the flash.
I should now Copy the new BIOS to the MEDUSA using my TL866II
Then Flash the MAC ROM with the medusa
Then Clean the ME region using the medusa

I still am unsure what all this has to do with a camera error code but I will give it a try.
Confirm my steps.
I have been reading about this for the last 3 hrs.
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Staff member
If you have the backup done, nothing bad can occur.
I hope you did verify backup reading already.

Do the steps mentioned, let see what happens...


OK did it.
Mac boots up but NDC001 camera error persists

I do have another full display assembly that I can swap out if it is in fact the camera itself that is the issue.
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