MacBook Pro A2251 Not turning on, 0.00-0.05A current draw at 5V repair

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MacBook Pro A2251 Not turning on, 0.00-0.05A current draw at 5V repair
Device	MacBook Pro A2251
Affects part(s)	Motherboard
Needs equipment	multimeter, soldering iron, soldering station
Difficulty	3. Hard
Type	Micro-Soldering, Soldering

Problem description

Diagnosing and resolving issues where a MacBook (820-01949) remains stuck on 5V with low current draw (~0.00–0.02 A) as indicated by a USB-C current meter. Commonly, this is attributed to a short to ground on the PPBUS_G3H power rail. Differentiate this from cases where one port reads 5V ~0.12–0.25 A while another reads 5V ≈5V 0.02 A (CD3217 issue), and where all ports show 5V ~0.00–0.02 A (PPBUS_G3H issue or T2 corruption).

Symptoms

• MacBook not turning on and is stuck on 5V with low current draw (~0.00–0.02 A) as measured by USB-C amp meter.
• Absent PPBUS_G3H voltage due to a short or creation problem.
• Device stuck in DFU mode due to corrupt T2/BridgeOs firmware.
• Absent or shorted PP3v3_G3H_RTC voltage.
• Failed CD3217 USB C controller (U3100_T, U3100_X, U3100_W, U3100_R)
• Short to ground on any of the power rails generated by U7800 that power the T2 chip, such as PP1v8_SLPS2R or PP1v1_SLPS2R.
• Missing U7800 input power
• Missing or shorted SLPS2R line. (Most commonly PP1v8_SLPS2R due to a short to ground.
• Non-specific areas of corrosion causing T2 or CD3217 communication issues.

Solution

Identifying the problem

Check for DFU or Recovery Mode:

• Connect the MacBook to another Mac via the master port and use Apple Configurator 2 to verify if it's in DFU mode.
• If in DFU mode, proceed to "Device stuck in DFU mode due to corrupt T2 firmware" repair steps.

Check PPBUS_G3H Voltage:

• Measure voltage on PPBUS_G3H (C6584 or similar) using a multimeter.
• Compare measured voltages to reference ranges.
• Interpret results based on voltage values and proceed to appropriate repair steps.

Check PP3v3_G3H_RTC Voltage:

• Measure PP3v3_G3H_RTC on a capacitor or resistor near CD3217 (C3100_W recommended).
• Compare measured values to normal range (~3.3V).
• Proceed based on measurement results.

Check PP3v3_G3H_PMU_VDDMAIN Voltage:

• Measure PP3v3_G3H_PMU_VDDMAIN on a capacitor near U7800 (C78B0 recommended).
• Compare measured values to normal range (~3.3V).
• Interpret results and proceed as necessary.

Solving the problem

Device Stuck in DFU Mode Due to Corrupt T2 Firmware:

• Revive T2 firmware using Apple Configurator 2 on another Mac.
• Follow steps to restore firmware, ensuring macOS is updated.

PPBUS_G3H Short to Ground:

• Inject ~1V with 5A limit into PPBUS_G3H using DC power supply.
• Localize shorted component using thermal imaging or isopropyl alcohol method.
• Replace the identified shorted component.

PPBUS_G3H Absent or Low with No Short:

• Check if PPDCIN_G3H is reaching ISL9240 (U7000).
• If not, proceed to "CD3217 troubleshooting" if no short is found.

CD3217 Troubleshooting:

• Check current sensing resistors: R7021, R7022, R7061, R7062.
• Replace ISL9240 and associated resistor if needed.

PP3v3_G3H_RTC Low or Absent:

• Diagnose possible shorted capacitor around CD3217 or from CD3217 itself.
• Check GHGR_EN_MVR signal produced by ISL9240 (U7000).
• Replace ISL9240 (U7000) if enable signal is missing.

PP3v3_G3H_PMU_VDDMAIN Low or Absent:

• Check R7900 resistor: ensure power to pin 1 and measure voltage on pin 2.
• Replace R7900 and retest if resistance is out of spec.
• If needed, investigate R6934/35 resistors for blowing.