A2991 820-02935 IPD_SYS_AWAKE Missing

Working on an A2991 board that had an overvoltage on 1v2_s2 which killed several components on that rail, including UG400, UG260, UG090, and UJ120. I restored power and the board seemed to work well; however, when I DFU restored it to install MacOS Tahoe, the board fails DFU with error 1 (no trackpad connected).

I found pin 9 of JT400 (IPD_SYS_AWAKE_CONN) completely missing (0v) and not shorted (.340 diode). This is a tiny circuit, and I found all inputs/vcc for UT320 to be present. Just to see how the board would act, I ran a wire from pin 1 to pin 3 just to see if having the 3.3v at the trackpad connector would allow DFU to complete, but it did not. I am missing IPD_SYS_AWAKE and it comes directly from the SOC. Is there any other signal that is in-sequence with IPD_SYS_AWAKE that I can piggy-back to UT320? Again, the unit worked perfectly (for a few weeks, even) before DFU-restore; the trackpad itself even works fine (during DFU), it just fails restore.

Is there anything I can check or try in this case, or has the SOC been damaged by the ripple on 1v2_s2 from the failed capacitor? The capacitor failed enough to kill components near it on the 1v2_s2 rail, so I am worried it reached the CPU/SOC.

Any input or thoughts appreciated!

Mentioned capacitor didn't kill anything; it failed because of overvoltage on 1V2_S2 power rail, like all other chips.

You should try several times DFU restore.
If trackpad worked before attempting the restore, there should't be any hardware problem.

Thank you!

Have tried DFU in multiple cases probably 50 times at this point. I have attached the exact error that happens every time. Also, I will mention: The error happens well-into the DFU restore; the Apple logo appears and progress bar at bottom of screen reaches ~80% done before the error occurs. Also, trackpad is clicking fine at the time when DFU fails.

Also: Why would only 4-5 chips be killed on 1v2_s2, but so many others not be affected? I would expect an overvoltage large enough to STG several chips would damage more on the circuit? Only chips attached to PP1v2_ATCRTMR2_VDDIO were killed, so the overvoltage must have occurred on that subcircuit correct?

UG400 is directly connected to 1V2_S2.

What is IPD_SYS_AWAKE voltage level on working board?

IPD_SYS_AWAKE is 3.3v on a working board, and it's present at all times. On this board, it never appears or pulses or anything at all.

"I ran a wire from pin 1 to pin 3"
Pin 4 went high then?

Check IPD_LID_OPEN_1V8 and IPD_WAKE_CONN_L; compare with good board.
BTW, check JT400 signals when trackpad is connected.
I hope its power rails are all good.

Yes, pin 4 went high as-normal and I got signal at JT400 normally then as well, but the DFU failed *exactly* the same way. Diode reading is also NORMAL on IPD_SYS_AWAKE (.340) as compared to working board, so it's not shorted.

Every other pin at JT400 is normal/present compared to a working board. I DID NOT check IPD_SYS_AWAKE with a trackpad connected, however, on a working board, IPD_SYS_AWAKE is present *without* trackpad connected. So, I would expect it should be present without trackpad connected on this bad board as well, but I will measure with trackpad to be sure and to see if any change in behavior.

Will check LID signals well again but every other signal was present/normal when checked initially, including all LID signals.

Thank you again for your help, it means a lot and is very appreciated.

"IPD_SYS_AWAKE is present *without* trackpad connected"
In such case, CPU is the one which first wakes up the trackpad.

Seems that even you force on the trackpad, CPU doesn't talk with it.
I suppose that CPU can't start such communication, without sending AWAKE signal by itself.