820-00850, stuck at 20V, 0A, not powering on

[KootenayMacGuy]

Hi there

I have a A1989, 820-00850 board that is not powering on. When i plug in the charger it switches from 5V to 20V, 200-300millamps for about 4-5 seconds and then drops to 0 milliamps. It stays like this for about 10 seconds and then goes back up to 200-300 milliamps, 20V for a few seconds again and then back to 0ma again. It never fully powers up. I have gone over all the usual power rails and the only ones that seem to be missing are PP1V8_S5 and PP1V8_S3.

Machine will not boot into DFU mode (I have tried 20 or so times)

Could this be a T2 chip issue? The MacBook died during a software update (and firmware update, of course) There is absolutely no liquid or corrosion. The board is mint.

If its a T2 Issue, I did get my hands on a T203 programmer, I havent used it yet. I am just not sure if it can be used to repair the firmware issue, if that is the issue.

Any help is appreciated

 

[2informaticos]

T203 only helps with SoC ROM flashing.
Only DFU can help with T2 firmware.

Be sure you follow all the steps in the DFU process.
Check if all AWAKE, SLPS2R and SSD voltages are present.

 

[KootenayMacGuy]

Alll AWAKE, SLPS2R, and SSD voltages are good except for:

PPVDDCPU_AWAKE is 0.933V instead of 1.06v

PPBUS_G3H is 12.62V. Is this too low?

 

[2informaticos]

"PPVDDCPU_AWAKE is 0.933V instead of 1.06v"
Did you check it at the output pin of the coils?

Did you try DFU again, following the tutorial steps?

 

[KootenayMacGuy]

I followed the DFU mode exactly, about a dozen times, with two different cables on three different Macs, with and without power and with and without battery conected (POWER, L-OPTION, L-CONTROL, R-SHIFT, 8 seconds) . The host mac does see the device as a USB device, it just the target Mac refuses to go into DFU mode.

PPVDDCPU_AWAKE is .933V at the coils.

 

[2informaticos]

Ooops, just saw PPVDDCPU_AWAKE is not specified to be 1.06V.
There is a range 0.625V-1.06V; so 0.93V looks good.

T2 must have an internal problem, if machine can't enter DFU.
Considering that all necesary voltages are present.