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 ◉◉◉◌ Hard
Type Soldering


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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

Diagnostic Steps

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.

Repair Steps

Device stuck in DFU mode due to corrupt T2 firmware

  • Revive or restore T2 firmware via Apple Configurator 2.
  • Ensure you're running the latest macOS version for consistent results.
  • Follow the provided Apple support article for the procedure.
  • You should see a big square icon pop up that says "DFU" or rarely, "RECOVERY". Click the icon, Navigate to the top menu bar click "Actions" then "Advanced". Select Revive device. You will see a progress bar appear. This process can take anywhere from 2 minutes to over 30 minutes in some cases. It is important to note, if the device is in Recovery mode, the end user may have brought the device to another repair shop or Apple first, who attempted a DFU revive which failed. You may have a secondary issue if the revive fails again.
  • SELECTING RESTORE WILL WIPE ALL USER DATA!
  • Possible causes for a device to fail a DFU revive:
    1. Short to ground on PP2v5_NAND_SSD_0
    2. Absent U9000 voltages. (PP0v9_SSD_0, PPVCCQ_ANI_SSD0 (1.8v) )
    3. Failed Trackpad (Will almost always show the Apple logo before failing the process.)
    4. Failed NAND
    5. Failed T2 or T2 RAM.
    6. Cracked solder joints under T2 chip (Uncommon, usually only suspected if device was dropped prior to initial failure.)

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

PPBUS_G3H is created by the Intersil/Renesas ISL9240 (U7000) which is a buck or boost converter depending on its input voltage. If USB-C voltage is 5 V, the ISL9240 will boost the 5 V input to ≈12 V. If USB-C voltage is 20 V, the ISL9240 will buck (lower) the 20 V input to ≈12 V.

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

CD3217 Troubleshooting

If you are getting 5 V on PPDCIN_G3H, the ISL9240 is likely the cause of the problem, however we still need to check a few things before replacing the chip. The ISL9240 relies on a series of current sensing resistors to measure the amount of power being used by its output rail, PPBUS_G3H. If one of these resistors is blown, the chip will think that something on the output is pulling too much power, and it will disable itself as a protection measure.

  • Check current sensing resistors: R7021, R7022, R7061, R7062.
    • Their values are all 1Ohm
  • Replace ISL9240 if the resistors are normal.

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.
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