820-03286 (Air A3114 2024 M3) with no keyboard/trackpad

[sekidata]

This A3114 had significant liquid damage to the upper right corner of the logic board, affecting the entire trackpad circuitry. Machine appeared functional except no trackpad and no keyboard functionality. I cleaned corrosion and replaced around 15 affected components from a A2941 donor board. The trackpad connector JT400 had a bad pin for IPD_SYS_AWAKE_CONN, which I replaced by running a wire.

The trackpad is now recognized and tracks. However, haptic feedback is nonfunctional and the keyboard shows no signs of life (no Caps Lock light). All power rails going to the trackpad tested good (3.3/5.1/12V).

Connecting a good keyboard did not change anything. I’m using a new trackpad and cable for testing. And I’m testing with the LAS cable unplugged (IPD_LID_CLOSED_L is 1.2V).

 

[2informaticos]

Keyboard can't work without good trackpad.
You should test with known good (compatible) trackpad board/flex.

 

[sekidata]

I have tried four different A3114 and A2941 trackpads and the results is the same for all: The cursor tracks movement and I can select but there is no haptic feedback and the keyboard is dead. I believe the issue is logic board related.

 

[2informaticos]

Check all components and signals from page 94.

 

[sekidata]

A first pass inspection of page 94 (Trackpad Support) revealed no abnormalities. I'm comparing to an A3113 board since the trackpad circuitry is identical.

Specifically, what would explain the presence of tracking but lack of haptic feedback and keyboard function? A faulty INT line? A bad CLK line? A problem with the SCL/SDA bus lines?

 

[2informaticos]

Keyboard connects with trackpad through I2C_KBD_SCL/SDA.
But keyboard has its electronics which may fail; apart of tracking problem with corresponding SCL/SDA lines processing.
Incompatible KB/TP may also occur.

For the feedback, TP requires PPBUS_AON.
Just in case, check if this function isn't disabled by software.

 

[sekidata]

All SCL/SDA lines are properly pulled up. I made sure that PPBUS_AON (12V) is present on the trackpad itself. I also tried a replacement daughter board and keyboard. No change.

Software enable for haptic is on. I’m going to run a DFU Restore just to make sure that there’s no underlying firmware issue.