2022 820-02536 Air board with restarting issue (A2681)

[sekidata]

This A2681 2022 board came in with liquid damage in the PP5V_S2 area and some other small spots. After cleaning, I replaced a misbehaving UC300 and the machine now chimes and starts up. Trackpad and keyboard are nonfunctional, but I’ll troubleshoot that separately.

The main issue is that whenever I plug in or unplug a USB-C charger, the board restarts. Happens for all 3 USB ports. I’ve never seen this behavior before; what could cause this?

 

[2informaticos]

Check if any CD3217 chip has short, or low resistance, between VBUS and PP_5V0.

 

[sekidata]

All three CD3217s show >1MΩ between PPVBUS_USBCx and PP5V_S2.

 

[2informaticos]

What is PPBUS_AON behavior?
Did you test with charged battery?

 

[sekidata]

All tests were done with battery connected; that's how I found out that the board restarts with every plug/unplug of the charger cable.

PPBUS is 12.3V, then as the Apple logo shows it drops to 12.0V.

The startup process is interrupted by either USB-C resetting spontaneously, or by unplugging the charger cable (both cause a restart). Sounds like a short somewhere.