MacBook Pro M4 Pro 2024 (A820-03400-5) – Keyboard not detected, all rails check out – Suspect UT102 (TCAL6416) internal VCC-VCP leakage

[macfix_hh_25]

Hi everyone,
i got a MacBook Pro M4 Pro 2024 (820-03400-5) with following problems:
– Keyboard not detected, all rails check out – Suspect UT102 (TCAL6416) internal VCC-VCP leakage
Working with schematics for 820-02918 (M3 Pro) as no schematics for 820-03400-5 are available yet. Most signal names and topology appear consistent.

Board background: Board came in with severe physical damage – bent chassis, bent keyboard and multiple sharp impacts on the display. Original symptoms: starting but black display, not starting with good known new display, dead keyboard, WiFi chip running hot+not working, no charging detected.

Resolved so far:

• UL000 (WiFi/BT) was internally shorted on PP1V8_S2 (7.1Ω to GND, 1.79V holding stable, 90°C operating temperature, only the chip itself was hot – not the surrounding caps). Removed UL000 → PP1V8_S2 short cleared
• New UL000 installed, properly unbound/bound LB Tools programmer
• Display works with a new known-good display assembly.
• Trackpad fully functional.

Remaining issue – internal keyboard does not work:
Tested with new known-good keyboard and with a separate complete chassis/keyboard assembly – same result. Confirmed not a cable, connector, or keyboard-side defect.

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Measurements (all with board powered unless noted):

Measurement point	Value	Status
PP3V3_S2_HOLD_IPD @ CT120	3.28V	✓
PP1V85_S2_HOLD_KBD @ CT113	1.83V	✓
JT200 pin 2 (PP1V85_S2_HOLD_KBD)	1.83V	✓
JT200 pin 34 (PP3V3_AON_KBD_CONN)	3.28V	✓
UT101 RESET* @ CT111	3.25V	✓ HIGH (out of reset)
UT102 RESET* @ RT120	3.25V	✓ HIGH (out of reset)
I2C_KBD_SCL @ RT123	3.28V	✓ idle high
I2C_KBD_SDA @ RT124	3.28V	✓ idle high
IOXP1_INT_L @ RT125	2.98V	Slightly pulled
IOXP2_INT_L @ RT112	2.98V	Slightly pulled
IOXP2_ADDR	1.83V	✓
KBD_DRIVE_Y0 @ JT200 pin 10	0.00V	No scan activity
KBD_SENSE X6/X7/X9/X11 etc.	1.81V	Pull-up idle state

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Suspected root cause – UT102 internal VCC-VCP short:
The pin 23 that should carry IPD (~1.85V) on UT102 reads 3.28V instead.
Resistance measurements with board off:

• CT122 pin 1 (PP1V85_S2_HOLD_KBD) to GND: 250Ω
• CT120 pin 1 (PP3V3_S2_HOLD_IPD) to CT122 pin 1: 158Ω

A 158Ω path between the 3.3V VCC rail and the 1.85V VCP rail with the board off indicates an internal leakage inside UT102 between its VCC and VCP pins. Because UT108 (LP5907SNX-1.825) is an LDO and cannot sink current, this leakage pulls VCP up to VCC potential. Result: all GPIO I/O levels of UT102 swing at 3.3V instead of 1.8V, which the SoC's keyboard interface cannot communicate with.
This is consistent with internal die damage from the impact – everything passive measures correctly but the chip's internal level-shifting reference is corrupted.

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Planned next step: Replace UT102. Before replacement, planning to verify UT101 doesn't have the same defect by measuring CT110 to CT113 resistance.

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Questions for the forum:

1. Has anyone seen this specific failure mode (VCC-VCP internal leakage on TCAL6416) on impact-damaged M-series boards or is it just a different rail /pin conncetion?
2. Could it be that M4Pro has a different keyboard connector then M1- M3? (only tested with M1 Pro Keyboard as good known keyboard)
3. Is my interpretation of the LDO not being able to sink current correct, or am I missing something obvious?
4. Are there any other measurements I should take before committing to the UT102 replacement?
5. On M4 Pro (820-03400-5) – has anyone confirmed whether the pin assignment for UT102 matches the M3 Pro reference schematics, or are there changes I should be aware of?

Open to any input. Thanks in advance.