This is what i originally though as well, I will double check this today. I also asked the client to bring me a new trackpad for this model specifically. They brought it to me like this an di do not have a spare to test with so they are bringing me one today.

The ppbus AON lines are the ones shorting all kinds of stuff on this unit so what you are saying totally makes sense.

UPDATE: part number is 821-02853 which is for a late 2020 year model. thank you for bringing this to my attention.

Original fault was customer spilled milk on unit, no corrosion was found on the board. Took mainboard out of original case and LCD and swapped it into the fully functioning case and LCD.

Shorts show up all over the board when trackpad is connected only. Trackpad is used and fully functioning from another unit of same model. Voltage injection causes trackpad connector to get hot but nothing else, swapped on board connector to rule that out, same issue. Diode reading on IPD_MCU_INT_CONN is higher then reference board @ .935 expected is .803. Shorts show up on PPVBAT_AON_CHGR_REG and...

Awsome thank you!

Yea, i found a short on pp3v3_upc_xb_ldo and the chip got hot in this area on injection. Original symptoms were 5v no switch to 20v, one port took 5v and .14 amps other port took 5v no amps.

Macbook

If i take CD321500 from another board and swap both chips from cd521500Z to cd321500 will this work or is there another chip that needs to be swapped with the pair? I am checking now if my partner has a doner board, but i was just curious.

I know they have to be matched to work.