A2141 2019 16" MacBook Pro

{|class="wikitable" ! style="text-align:left;"| Problem ! Solution
 * No Power, 5v and 0.00-0.05 as measured on a USB-C amp meter
 * It is very common on the 820-01700 for U9080 or U9580 to fail in a way that shorts PPBUS_G3H to PP2v5_SSD1 or PP2v5_SSD0. When this happens, the NAND chips (SSD) will usually becoming damaged in a way that makes data recovery impossible. If you find U9080 or U9580 to be corroded, damaged, burned or the cause of a PPBUS_G3H short to ground, remove it and check resistance on PP2v5_NAND_SSD1/0. You should have greater than 60Ω to ground. Most boards will have greater than 1k Ω to ground as measured by a digital multimeter with the board at room temperature.
 * It is very common on the 820-01700 for U9080 or U9580 to fail in a way that shorts PPBUS_G3H to PP2v5_SSD1 or PP2v5_SSD0. When this happens, the NAND chips (SSD) will usually becoming damaged in a way that makes data recovery impossible. If you find U9080 or U9580 to be corroded, damaged, burned or the cause of a PPBUS_G3H short to ground, remove it and check resistance on PP2v5_NAND_SSD1/0. You should have greater than 60Ω to ground. Most boards will have greater than 1k Ω to ground as measured by a digital multimeter with the board at room temperature.

Possible diagnoses for 5 V and low current draw as indicated on the USB-C current 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_X voltage.

• Failed PP2v5_NAND controller (U9080 or U9580)

• Failed CD3217 USB C controller

• 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.) (Rare on this board.)

• Non-specific areas of corrosion causing T2 or CD3217 communication issues.

➤Diagnostic Steps

1. Check if the device is stuck in DFU or Recovery mode.

- Plug the MacBook into another Mac or MacBook via its master port (Left side, bottom port, closest to the trackpad) and open Apple Configurator 2 to verify that it is or isn't in DFU mode. If the device is in DFU mode, Proceed to "Device stuck in DFU mode due to corrupt T2 firmware" in repair steps below.

'''2. Check voltage on PPBUS_G3H. - Normal Diode Mode Reading: ~0.410'''

To accurately measure voltage on PPBUS_G3H, set your multimeter to DC voltage mode and place the black probe to ground and the red probe on PPBUS_G3H. For the 820-01987, the ideal measurement point is F7000.

~12.60–12.65 V = Normal

~12.28–12.35 V = T2 not booted. The likely cause for this is the device is stuck in DFU mode due to corrupt T2 firmware or a failed CD3217. If the board is not in DFU mode proceed to checking below items. Proceed to repair steps below for corrupt T2 firmware if the device is found to be in DFU mode.

~0 V = Short to ground or absent voltage due to a creation problem. Proceed to repair steps below for shorted or absent PPBUS_G3H voltage.

'''3. Check PP3v3_G3H_RTC_X voltage. - Normal Diode Mode Reading: ~0.420'''

- Ensure your multimeter is in DC voltage mode. ( Straight line with 3 - - - under the line. ) Place the black probe on ground and the red probe on PP3v3_G3H_RTC_X. It is recommended to measure PP3v3_G3H_RTC_X on a capacitor or resistor near one of the CD3217s to rule out a trace/via issue. C3100 is a good place to measure this line on the 820-01700 logic board.

~3.3 V (3.290–3.425 V) = Normal.

If PP3v3_G3H_RTC_X is missing, check for a short to ground by putting your multimeter in continuity or resistance mode, the value should be fairly high, with most boards sitting above 1k Ω. Occasionally you can have a false positive for a short to ground due to capacitance on the line. If this is the case, resistance to ground will be around 60Ω. If this is the case, let the board sit with power disconnected for a few minutes then recheck.

Proceed to PP3v3_G3H_RTC_X low, absent or shorted repair steps below if a problem is found.

'''4. Check PP3v3_G3H_SOCPMU voltage. - Normal Diode Mode Reading 0.378'''

- Ensure your multimeter is in DC voltage mode. ( Straight line with 3 - - - under the line. ) Place the black probe on ground and the red probe on PP3v3_G3H_SOCPMU. It is recommended to measure PP3v3_G3H_SOCPMU on a capacitor near U7800 to rule out a trace/via issue. C7893/C7869 is a good place to measure this line on the 820-01700 logic board.

~3.3 V (3.290–3.425 V) = Normal.

If you measure 0v on this line, you are likely missing PMU_PVDDMAIN_EN which enables U7650 to output this line, this is usually due to R7900 being blown or otherwise damaged. If R7900 blows after replacement, replace U7800 and R7900.

Values below the above spec should be considered abnormal. Proceed "PP3v3_G3H_SOCPMU low or absent" in the repair steps below.

➤Repair Steps

Device stuck in DFU mode due to corrupt T2 firmware:

- Revive T2 firmware via Apple Configurator 2.

NOTE: You must be running the latest version of MacOs for this to work consistently. Check for MacOs updates prior to reviving/restoring T2 firmware.

How to revive T2 firmware: Plug the device you are working on to another Mac or MacBook via its master port. The master port on the A2141 is the bottom left side USB-C port (closest to the trackpad.) If you are confused, please see the diagram listed on Apple's how to page - https://support.apple.com/guide/apple-configurator-mac/revive-or-restore-an-intel-based-mac-apdebea5be51/mac

Once plugged in, open Apple Configurator 2. 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.

SELECTING RESTORE WILL WIPE ALL USER DATA!

PPBUS_G3H Short to ground:

Inject around 1 V with a 5 amp limit into PPBUS_G3H with a DC power supply. A larger tantalum capacitor or the main PPBUS fuse (F7000/F7001) is preferred to inject voltage to, as you will often need a lot of current to be pushed into the line to cause the shorted component to heat up. 1 V is usually sufficient. It is not recommended to inject over 1 V as if one of the CPU VRMs or U9080/U958 0is shorted, you will end up killing the CPU or SSD. A good place to inject voltage to on the 820-01700 is F7000 or F7001.

With voltage being injected, perform thermal imaging of the board. If thermal imaging is not available, feel around the board to see where it is getting warm. Once the area is localized, add a small amount of isopropyl alcohol to the area to localize the shorted component.

Once the shorted component is localized, replace the shorted component.

'If U9080 is the cause of the short, check resistance to ground on L9081, you should have greater than 60 ohms, ideally having more than 1k ohms. If you measure 1-3 ohms, the NAND ICs (SSD) are likely dead.'

'If U9580 is the cause of the short, check resistance to ground on L9581, you should have greater than 60 ohms, ideally having more than 1k ohms. If you measure 1-3 ohms, the NAND ICs (SSD) are likely dead.'

Normal Diode Mode reading on PP2v5_NAND_SSD0 and PP2v5_NAND_SSD1 is around ~0.400-0.500.

For more info on finding short circuits, please see - [2]

PPBUS_G3H Absent or low with no short:

If PPBUS_G3H is absent, first check that PPDCIN_G3H is making it to the Intersil/Renesas ISL9240 (U7000). Measure PPDCIN_G3H (Normal diode mode reading is ~0.550) with a multimeter in voltage mode at C7024, C7043, C7027, or C7026 on 820-01700. The voltage should match that of the USB-C amp meter (5 V). If 0V is read, check for a short, and if none is found, move to "CD3217 troubleshooting" in the repair steps. If 5 V is read, check the current sensing resistors (listed below) as the ISL9240 may have shorted internally causing the current sensing resistors to blow. Place the multimeter probes on each side of the resistors to measure the resistance, which should be within 5–10% of the reference. If a resistor is found out of spec, replace it and the ISL9240, as the resistor likely blew due to an internal short. Depending on the input voltage, the ISL9240 either buck or boosts the voltage to ~12 V; if USB-C voltage is 5 V, it boosts it

R7021 — 1.00 Ω

R7022 — 1.00 Ω

R7061 — 1.00 Ω

R7062 — 1.00 Ω

If the current sensing values are normal, replace the ISL9240 (U7000).

PP3v3_G3H_RTC_X low or absent:

The PP3v3_G3H_RTC_X voltage powers the "brain" of the CD3217 USB-C controllers, enabling communication with the USB-C charger to allow for 20 V. If PP3v3_G3H_RTC_X is shorted, low, or absent, the communication between the charger and the device cannot take place, resulting in the device being stuck at 5 V. On the 820-01700, the buck converter U6960 is responsible for lowering the voltage from PPBUS_G3H (approximately 12 V) to 3.3 V to generate PP3v3_G3H_RTC. Therefore, in order to get PP3v3_G3H_RTC, PPBUS_G3H must be obtained first.

•The most common reason for PP3v3_G3H_RTC to be missing or low, is a short to ground, usually on a capacitor around one of the CD3217s, or from a CD3217 itself. If a short to ground is measured, inject voltage at R6935/35 and perform relevant short detection strategies. for more info on finding short circuits, please see - Detecting short circuits

•If PP3v3_G3H_RTC_X is not shorted, confirm that the enable signal GHGR_EN_MVR is present, which is generated by the ISL9240 (U7000). The ISL9240 often fails in such a way that prevents GHGR_EN_MVR from being produced. If the enable signal is missing, replacing the ISL9240 (U7000) is recommended. Additionally, due to the capacitance of the circuit, PP3v3_G3H_RTC_X may falsely read as short, measuring around 60-100 ohms. This should be considered a false positive. To confirm, remeasure the PP3v3_G3H_RTC_X after the board has been removed from power for a few minutes.

•PP3v3_G3H_RTC can also be pulled low by PP3v3_UPC_XA LDO, PP3v3_UPC_XB_LDO, PP3v3_UPC_TA_LDO or PP3v3_UPC_TB_LDO, so if you have no measurable short to ground, and your enable/VIN is present, check all the listed rails for a short or low resistance to ground. Low resistance to ground/short on the above LDO lines will usually be caused by a bad CD3217. If a short is found on one of these lines, inspect capacitors on the relevant line for cracks, corrosion or discoloration. If none is found, remove the corresponding CD3217 and remeasure to see if the short is resolved. If the short is measured to be resolved, replace the CD3217. You must source the replacement chip from another 820-01700.

• Occasionally, U6960 may PPBUS_G3H to ground and may blow it's VIN current limiting resistor R6900. Be sure to check voltage on both sides of R6900 if you suspect your VIN may be missing to U6960.

'''If you found and resolved a short circuit, and still have low voltage on PP3v3_G3H_RTC, check voltage on both sides of R6934/35. These resistors can blow in response to a short circuit.'''

PP3v3_G3H_SOCPMU low or absent

If U7650 is not visibly corroded, it is very unlikely that it is the cause of the failure. U7650 must be told to turn on PP3v3_G3H_SOCPMU by the PMU_PVDDMAIN_EN signal which can be measured on R7652. In most cases, it will be missing.

If PMU_PVDDMAIN_EN is missing, and PP3v3_G3H_RTC_X is present, measure voltage on BOTH SIDES of R7900. Occasionally due to a trace issue, PP3v3_G3H_RTC will not make it to the resistor, other times, the resistor may be blown. If voltage is low on pin 2, replace the resistor and test the board. If the resistor blows again, replace U7800 and R7900 again, as U7800 is likely pulling too much current and blowing the resistor.

Other faults causing PP3v3_RTC_G3H_SOCPMU to be missing are rare, but can be related to U7650 and corresponding components. If PMUVDDMAIN_EN is present, check for a short to ground on PP3v3_RTC_G3H_SOCPMU, PP3v3_G3H_T and PP5v_S5_LDO.


 * No Power, 5v and ~0.23-0.31A, Cycling or static.
 * Possible Diagnoses for No power, 5v and ~0.23-0.31a, cycling or static as measured on a USB-C amp meter:Always check to see if all 4 ports are reading the same, often times you'll find one port is doing something different. If this is the case, the issue is likely related to the CD3217 or its corresponding circuitry tied to that port.
 * Possible Diagnoses for No power, 5v and ~0.23-0.31a, cycling or static as measured on a USB-C amp meter:Always check to see if all 4 ports are reading the same, often times you'll find one port is doing something different. If this is the case, the issue is likely related to the CD3217 or its corresponding circuitry tied to that port.

• Failed or corroded CD3217.

• Corroded resistors around CD3217.

• Corroded TBT ROM or corresponding resistors or traces.

• Device stuck in DFU mode

• Shorted or missing PP2v5_SSD1 or PP2v5_SSD0 voltage

• Missing U7800 (PMU) output voltage

.

➤Diagnostic Steps:

1. Check if the device is stuck in DFU or Recovery mode.

- Plug the MacBook into another Mac or MacBook via its master port (Left side, bottom port, closest to the trackpad) and open Apple Configurator 2 to verify that it is or isn't in DFU mode. If the device is in DFU mode, Proceed to "Device stuck in DFU mode due to corrupt T2 firmware" in repair steps below.

2. Check both ports to see if one port cycles or has a different amp draw. If one port cycles, or has a different amp draw than the others, the offending CD3217 is likely tied to this port.

**LEFT SIDE BOTTOM PORT IS CONTROLLED BY U3200

**LEFT SIDE TOP PORT IS CONTROLLED BY U3100

**RIGHT SIDE BOTTOM PORT IS CONTROLLED BY UB300

**RIGHT SIDE TOP PORT IS CONTROLLED BY UB400

- In the presence of CD3217 issues, you will almost always find one port reading differently; with the most common finding being cycling.

3. Visually inspect USB-C controllers listed above for corrosion or other visual signs of damage. Address as necessary.

4. Visually inspect TBT ROMs (U2890 and UB090) for corrosion or other signs of damage. If corroded, TBT ROMs usually do not have to be replaced. Lift, and clean pads if necessary and replace any corroded resistors. Run jumpers as needed.

➤Repair Steps

Device stuck in DFU mode due to corrupt T2 firmware:

- Revive T2 firmware via Apple Configurator 2.

NOTE: You must be running the latest version of MacOs for this to work consistently. Check for MacOs updates prior to reviving/restoring T2 firmware.

How to revive T2 firmware: Plug the device you are working on to another Mac or MacBook via its master port. The master port on the A2141 is the bottom left side USB-C port (closest to the trackpad.) If you are confused, please see the diagram listed on Apple's how to page - https://support.apple.com/guide/apple-configurator-mac/revive-or-restore-an-intel-based-mac-apdebea5be51/mac

Once plugged in, open Apple Configurator 2. 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.

SELECTING RESTORE WILL WIPE ALL USER DATA!

If one port acts differently than the rest:
Device not in DFU mode:

Important diode mode readings:

CD3217 1.5v Core LDOs

PP1V5_UPC_TA_LDO_CORE: ~0.500

PP1V5_UPC_TB_LDO_CORE: ~0.500

PP1V5_UPC_XA_LDO_CORE: ~0.500

PP1V5_UPC_XB_LDO_CORE: ~0.500

CD3217 3.3v LDOs

PP3V3_UPC_TA_LDO: ~0.480

PP3V3_UPC_TB_LDO: ~0.480

PP3v3_UPC_XA_LDO: ~0.480

PP3V3_UPC_XB_LDO: 0.480

If liquid damage is suspected: Check PP1v5_UPC_LDO_CORE and PP3v3_UPC_LDO lines for shorts to ground around the CD3217 of the port that is displaying different readings than the rest (See above.). If a short to ground is identified, remove and replace the corresponding component, which may be a capacitor or the CD3217 itself. If the CD3217 is found to be faulty, replace the chip associated with the port in question. Heat-induced delamination of the CD3217 is commonly observed, yet this typically does not affect the functionality or longevity of the IC. Additionally, all surrounding resistors should be inspected for corrosion and replaced if necessary. Lastly, pad damage should be examined for, particularly on lines fed by 3.3v, as this can often be overlooked and mimic a CD3217 issue. YOU MUST SOURCE THE REPLACEMENT CD3217 FROM ANOTHER 820-01700 DONOR BOARD.

If no liquid damage is found: '''
 * 1) Check for shorts to ground on both the PP1v5_UPC_LDO and PP3v3_UPC_LDO line around each CD3217 - If a short is found, inspect all capacitors tied to the shorted line. If damage is found (Corrosion, cracks or discoloration), replace the shorted capacitor, otherwise, replace the CD3217 tied to the shorted line.
 * 2) If no short is found, replace the CD3217 tied to the port acting differently than the rest.'''

Differential diagnosis for no display backlight on the 820-01700 logic board:
 * No Image
 * Check the LCD cable and the connector on both the screen side and the logic board side. The backlight power line is right next to the eDP data line for the image. Any minor corrosion here results in 50 volts or more going to the displayport mux, U9850. U9850 is what the dedicated GPU and the CPU's integrated GPU go to before it goes to the screen. When the U9850 does not work, you also wont get backlight.
 * No Display Backlight
 * Troubleshooting backlight issues on the 820-01700 is identical to all other USB-C MacBook Pro motherboards.
 * No Display Backlight
 * Troubleshooting backlight issues on the 820-01700 is identical to all other USB-C MacBook Pro motherboards.
 * Failed display TCON board.


 * Failed display LED strip.


 * Short to ground on backlight output caused by a failed output decoupling capacitor.


 * Failed backlight driver (U8400)


 * Backlight driver circuit fault (resistors, traces, capacitors, MOSFETs.)
 * Low voltage on PP5v_S0SW_LCD

The most common cause for a 820-01700 to have no backlight in the absence of liquid damage, is a short to ground on backlight output due to a failed capacitor.

Important relevant diode mode readings for troubleshooting backlight issues:

PPVOUT_S0_LCDBKLT_F: ~1.180

PPVIN_SW_LCDBKLT_SW: ~0.830

PP5V_S0SW_LCD: ~0.570

PP5V_G3S_BKLT_D: 0.410

PP5V_G3S_BKLT_A: ~4.10

➤Diagnostic Steps

1. Check for a short to ground on backlight output (PPVOUT__S0_LCDBKLT_F). C8471 or adjacent capacitors in the series is an appropriate area to measure, since it does not require removal of the system board. If a short to ground is measured, unplug the display connector to rule out a potential short to ground within the TCON board or LED strip of the display. If the short is persistent with the screen unplugged, proceed to the "Backlight output shorted to ground" repair steps below.

2. If no short to ground is measured, and there is no signs or history of infiltrative liquid damage to the system board, test the device with a known working display. If the device has backlight with a known working display, proceed to the repair steps below for "Device has backlight output on a known good display, but not on the originally installed display" below.

How to determine if U8400 is the cause of the backlight issue:

Failure of U8400 without the presence of liquid damage is uncommon, however if you have no backlight with a known good display, and do not have a short on backlight output, U8400 may be bad or you may have another circuit fault such as a bad resistor or broken trace within the U8400/backlight generation circuit.

If U8400 is corroded, replace it along with any other corroded resistors or capacitors adjacent to it.

It is also common for current sensing pins (pins 9 and 10) of U8400 to be very corroded with corresponding pad/trace damage. If this is the case, run a wire for each pad and connect them to the corresponding pins of R8400.

①. Ensure that the backlight circuit has its input voltage (VIN) by measuring on BOTH SIDES of F8400, which is the backlight fuse. Voltage on both sides of the fuse should be equivalent to PPBUS_G3H. If voltage is normal on both sides of the backlight fuse, proceed to the next step. The backlight fuse can blow in response to a previous short to ground in the backlight circuit, or due to the screen being plugged in without the battery disconnected. Rarely, the backlight fuse can become open (blown) due to development of sulfur deposits on the fuses' filament, or due to micro manufacturing defects on the fuses filament. If the backlight fuse is blown, check for a short on backlight output (PPVOUT_S0_LCDBKLT_F) and on backlight input (PPVIN_S0SW_LCDBKLT_F). If the fuse is blown, proceed to the "Backlight fuse (F8400) blown in the absence of a short to ground" repair steps below.

② Check that the backlight circuit is being enabled. The screen will need to be connected for the enable signal to be sent out. With the board on your bench, with a known good screen connected, measure voltage on pins 1 and 2 of R8442. You should have ~3.3v. Low voltage on pin 2 of R8442 is suggestive of an issue with U8400. If you have 0v on pin 1 of R8442, the backlight circuit is not being told to turn on, which raises the possibility of a CPU issue, or an issue with the display cable/connector.

③ Check the 5v inputs to U8400 (PP5v_S0_BKLT_D and PP5v_S0_BKLT_A).

PP5v_S0_LCDBKLT_D can be measured on R8444 and PP5v_S0_LCDBKLT_A can be measured on R8445. Be sure to check voltage on both sides of the resistor. If voltage is lower on one side of the resistor, R8444 or R8445 is likely blown, probably due to a short within U8400.

If PP5v_S0_LCDBKLT_D or A is low (Substantially lower than 5v), replace U8400 AND R8444/45 as R8444/45 acts as a current limiting resistor to protect PP5v_G3S, and likely blew as a result of an internal short within U8400.

If you have low voltage on pin 2 of R8442 with normal voltage on pin 1 of R8842, replace U8400.

If VIN, EN, and PP5v_S0_LCDBKLT_D are all present at normal levels, and you do not have backlight, replace U8400.

If EDP_BKLT_EN is missing, U8400 is NOT your issue.

➤ Repair Steps

Backlight output shorted to ground:

- Find and replace shorted component.

''Ensure the short is not caused by the display. Be sure to measure with and without the display connected.''

Most commonly, a short on backlight output is caused by a shorted capacitor. If you have a short on backlight output, solder a wire to a sturdy component that can handle a good amount of current, usually one of the backlight output capacitors (C8468 or C8461 is usually a good spot.) Inject 10v at 5 amps and thermally image the system board or deploy comparable short detection methods. For more information on short circuit detection, please see the following page - [10]

Device has backlight output on a known good display, but not on the originally installed display

- Replace the display assembly.

Backlight fuse (F8400) blown in the absence of a short to ground

- Replace the backlight fuse with a fuse from a donor board or a compatible replacement. (0603 package size, 3 amp, 32v fuse. Brand does not matter.)

''Before applying power be sure to double check for a short to ground. Check for a short to ground on backlight output and backlight input''.

• Failed T2 or NAND (Most likely diagnosis for most cases in the absence of the below causes.
 * No Power, 20v 0.03-0.08a
 * Differential diagnosis for no power, with 20v and ~0.03-0.08a as measured on a USB-C amp meter.
 * Differential diagnosis for no power, with 20v and ~0.03-0.08a as measured on a USB-C amp meter.

• Device stuck in Recovery mode due to prior failed DFU revive. (Most common.)

• Short to ground on PP3v3_S5.

• Corrupt T2/BridgeOs firmware.

• Failed PMIC (Rare.)

• Shorted or Absent SSD voltages.

• Corroded Ocarina PMIC. (U9000)

Relevant diode mode measurements:

PP2v5_NAND_SSD1: ~0.400-0.500

PP2v5_NAND_SSD0: ~0.400-0.500

PP3v3_S5: ~0.335

PP1v8_SSD1: ~0.380-0.450

PP1v8_SSD0: ~0.380-0.450

PP0v9_SSD0: ~0.400-0.500

PP0v9_SSD1: ~0.400-0.500

➤Diagnostic Steps

1. Check if the device is stuck in DFU or Recovery mode.

- Plug the MacBook into another Mac or MacBook via its master port (Left side, bottom port, closest to the trackpad) and open Apple Configurator 2 to verify that it is or isn't in DFU mode. If the device is in DFU mode, Proceed to "Device stuck in DFU or recovery mode due to corrupt T2 firmware" in repair steps below.

2. Check for a short to ground on PP3v3_S5.

- If a short to ground is found, proceed to the "PP3v3_S5 short to ground" repair steps below.

3. Check resistance to ground on PP2v5_NAND_SSD_0 and PP2v5_NAND_SSD`. (Normal values can be as high as >1MΩ or as low as 60Ω. In the case of SSD/NAND failure, resistance will usually be between 1-3Ω.)

4. Inspect U9000 for corrosion. The location of the chip on this board makes it prone to corrosion, either from liquid ingress or from condensation from dust collection. U9000 can be reballed if corroded which will likely resolve the issue if it is corroded.

➤Repair Steps

Device stuck in DFU mode due to corrupt T2 firmware:

- Revive or restore T2 firmware via Apple Configurator 2.

NOTE: You must be running the latest version of MacOs for this to work consistently. Check for MacOs updates prior to reviving/restoring T2 firmware.

How to revive T2 firmware: Plug the device you are working on to another Mac or MacBook via its master port. The master port on the A2141 is the bottom left side USB-C port (closest to the trackpad.) If you are confused, please see the diagram listed on Apple's how to page — https://support.apple.com/guide/apple-configurator-mac/revive-or-restore-an-intel-based-mac-apdebea5be51/mac

Once plugged in, open Apple Configurator 2. 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.

Possible causes for a device to fail a DFU revive:

- Short to ground on PP2v5_NAND_SSD_0 or PP2v5_SSD_1)

- Absent U9000 voltages. (PP0v9_SSD_0/1, PP1v8_SSD1/0(1.8v)

- Failed Trackpad (Will almost always show the Apple logo before failing the process.)

- Failed NAND

- Failed T2 or T2 RAM.

If no secondary causes are found, a DFU Restore may resolve the issue.

SELECTING RESTORE WILL WIPE ALL USER DATA!

PP3v3_S5 shorted to ground.

- Locate and replace the shorted component.

PP3v3_S5 is a tricky line to inject voltage to on this board, as most components are small 0201 parts. Be sure to use a small gauge wire to inject voltage if you choose to inject voltage to a 0201 part. The best place to inject voltage to on the 820-01700 is pin 5 of U4801.

1v at 5 amps is an appropriate voltage to inject into the line. The PCH can sometimes be the cause of a PP3v3_S5 short.

With voltage being injected, perform thermal imaging of the board. If thermal imaging is not available, feel around the board to see where it is getting warm. Once the area is localized, add a small amount of isopropyl alcohol to the area to localize the shorted component.

Once the shorted component is localized, replace the shorted component.

For more info on finding short circuits, please see - [4]

U9000 visibly corroded or damaged.

- If corroded, reball the IC. Replacement is usually not necessary.

- If physically damaged or burned, replace the IC. The IC is not programmed and can be taken from any board which utilizes the same part. (338S00410)

If no short is found on PP3v3_S5, and the device is not in DFU or recovery mode, and all other findings are negative, you can try forcing a firmware revive.

• Attempt to restore BridgeOs firmware via Apple Configurator 2 by placing the device into DFU mode. Solder a wire across SWK003 (Omitted/No Stuff) to pull SOC_FORCE_DFU high.

- STOP! Before you begin, is your Mac on the LATEST VERSION of MacOs? If not, update your system before proceeding. Forcing a MacBook into DFU mode, and attempting to restore BridgeOs firmware on a old version of MacOs may result in a bricked device.

NOTE: Selecting restore will wipe all user data.

➣ Follow the instructions on this Apple support article on how to revive or restore T2/BridgeOs firmware, including on how to force a Intel based MacBook into DFU mode by using a key combination. https://support.apple.com/guide/apple-configurator-mac/revive-or-restore-an-intel-based-mac-apdebea5be51/mac

If the device fails the firmware revive or restore, the T2 chip or one of the NANDs is likely dead or is receiving unstable power from the PMIC (U7800) causing it to crash. If the device fails the firmware revive, you can try empirically replacing U7800. You must removal the large shield covering U7800 and the T2 chip prior, which is not easy. You must use low melt alloy to remove the shield. Be careful not to bridge surrounding components. Go slow and be patient.

Replacing U7800 should be seen as a last ditch effort, as it only works in a small amount of cases, and does not have a definitive diagnostic test to determine if it is bad. •Failed capacitor causing a short to ground on PP2v5_NAND_SSD0
 * No Power, 20v ~0.10-0.15a
 * Possible Diagnoses for a 820-01700 with 20v on the charger and 0.10-0.15a as measured by a USB-C amp meter•Failed capacitor causing a short to ground on PP2v5_NAND_SSD1
 * Possible Diagnoses for a 820-01700 with 20v on the charger and 0.10-0.15a as measured by a USB-C amp meter•Failed capacitor causing a short to ground on PP2v5_NAND_SSD1

•U9080 or U9085 Failure

Relevant diode mode measurements:

PP2v5_NAND_SSD1: ~0.400-0.500

PP2v5_NAND_SSD0: ~0.400-0.500

➤Diagnostic Steps
 * 1) Check for a short to ground on PP2v5_NAND_SSD1 and PP2v5_NAND_SSD0. Normal diode mode readings are above.
 * 2) Perform high resolution thermal imaging to locate the fault.

If a short to ground is found, check U9080 and U9580 for signs of corrosion or burn marks. Often times you will find U9080/U9085 will have a "shadow" over a portion of the chip if it is bad. If this is seen, remeasure the line. If resistance/diode mode readings return to normal limits, replace the failed IC.

If U9080 and U9580 look good, inspect the capacitors on this line as they are commonly corroded due to dust. C9088, C9087, C9588 and C9586 are common culprits on this board.

➤Repair Steps

Remove and replace the shorted component.

If U9580 or U9080 is the cause of the short, be sure to check their relevant 2v5 power rails for shorts to ground. If you find one of the PP2v5_NAND_SSD lines reading 1-3 ohms to ground, the NAND chips are likely dead and the board is not practically repairable. If both PP2v5_NAND_SSD lines are within normal resistance and diode mode readings (See above) and the board still does not turn on, and displays a amp reading of 0.03-0.06, check to see if it is in recovery mode with Apple Configurator 2 and revive as necessary.

- Revive or restore T2 firmware via Apple Configurator 2.

''NOTE: You must be running the latest version of MacOs for this to work consistently. Check for MacOs updates prior to reviving/restoring T2 firmware.''

''How to revive T2 firmware: Plug the device you are working on to another Mac or MacBook via its master port. The master port on the A2141 is the bottom left side USB-C port (closest to the trackpad.) If you are confused, please see the diagram listed on Apple's how to page —'' https://support.apple.com/guide/apple-configurator-mac/revive-or-restore-an-intel-based-mac-apdebea5be51/mac

''Once plugged in, open Apple Configurator 2. 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.''

• Failed GPU • Failed Display (Unlikely) • Failed VRAM chip
 * Green or Purple Vertical Bars in display
 * Possible Diagnoses for Green or Purple Vertical bars on the display
 * Possible Diagnoses for Green or Purple Vertical bars on the display

➤Diagnostic StepsThe most important diagnostic test to perform, is checking to see if the machine properly displays an image on a KNOWN GOOD display. If the vertical bars are still present on a known good display, the issue is likely related to the GPU or VRAM.

Unfortunately, there is no definitive way to determine a VRAM fault from a GPU fault, especially since when this issue is present, the board usually will not boot into an OS. You can try heating the GPU at 100C for 3-5 min to see if the issue will temporarily resolve, if it does, the GPU is the cause of the issue. It is important to note that heating a flip chip at a low temperature for diagnostic purposes is not a solution, and will not "fix" the problem. Higher temperatures should not be used, as they can negatively affect the life of the chipset if it is not the problem. If no change in the problem is seen, the VRAM may be the issue. ➤Repair Steps- Based on your diagnostic findings, replace either the display, GPU, or VRAM.

If the GPU is the issue, you can reball one from a donor board as long as the proper tools are used. You should be using a BGA station, and you should not exceed 260C during the removal or replacement of the chip. Use 63/37 solder to reball the new chip. DO NOT REBALL THE OLD CHIP. THIS WILL NOT SOLVE THE PROBLEM. If the VRAM is the issue, replace all VRAM chips at the same time.
 * 20V, 0.040.07mA, PP3V3_S5 and PP1V8_S5 missing. PPBUS_G3H at 12.3V
 * The T2 chip is not properly communicating to the Calpe PMU (U7800), likely due to firmware corruption. This can also occur after replacing the PMU itself, or Ocarina, which is the SSD PMIC. Assemble the device and force it into DFU mode via the power button and keyboard.
 * The T2 chip is not properly communicating to the Calpe PMU (U7800), likely due to firmware corruption. This can also occur after replacing the PMU itself, or Ocarina, which is the SSD PMIC. Assemble the device and force it into DFU mode via the power button and keyboard.

Perform a revive via Apple Configurator 2. This spot on the board is VERY susceptible to corrosion with no liquid damage. It is placed in the path of incoming cooling air, so dirt and dust build up in this spot causing moisture to be retained, resulting in corrosion. Recommend a conformal coat on this area once repair is done. After removing the short and verifying PP2V5 is present you may find the no power is almost the same, but now taking 20V, 020mA. If the rest of the board passes visual inspection, and no other shorts are suspected, the next step is to DFU revive (*CAUTION* DFU Revive must never be mixed up with DFU Restore, DFU revive keeps data on the drive, DFU Restore erases all data)
 * No Power, PPBUS_G3H at 12.5V, charger at 20V cycling from 0300mA
 * Found C9586 for PP2V5_NAND short
 * Found C9586 for PP2V5_NAND short

DFU Revive: Place the logic board back into the machine connecting everything but the battery cable (you can screw the battery connector on just leave the cable disconnected, in a properly functioning battery disconnecting the cable isolates the battery from the board without the need to unscrew the connector)

On a working machine load "Apple Configurator 2" and have an Apple USBC charging cable ready. On your no power machine locate SWK003, this is a "no stuff" button for SOC_FORCE_DFU, it is next to the T2 chip below the keyboard connector. The process is you will short theses pads while connecting the power. You can solder a wire between them or use tweezers or a screwdriver. Now plug the charging cable between your machine running "Apple Configurator 2" and the "master" port on the no power machine (the left side closest to the trackpad). The middle of the "Apple Configurator 2" window should show a large box with the letters DFU in. Right click on the box and choose "advanced", and then "revive device". After some time the no power machine should start taking normal current and turn on. The box in "Apple Configurator 2" should change to a lock symbol.

Note: If the DFU logo comes up after shorting the pads and then goes off again in a loop, plug in a USB-C power adapter AS WELL as a USB-C cable connecting to the other Mac. This is generally needed if the battery is completely flat.
 * Keyboard keys sticking or not coming up properly as you press them
 * This machine uses the traditional "scissor switch" keyboard which is less prone to sticking issues than the infamous butterfly switch. If sticking occurs, try the MacBook keyboard troubleshooting guide.
 * No Power. No life on USB-C amp meter, or 5V ~ 0A.
 * Check PP3V3_G3H_RTC_X. This should be 3.3V. If you don't have this, check for short. If no short, check for input voltage on U6960; pin 1 of C6961 is a great point to test. If present, check enable signal. If good, replace U6960.
 * }
 * Check PP3V3_G3H_RTC_X. This should be 3.3V. If you don't have this, check for short. If no short, check for input voltage on U6960; pin 1 of C6961 is a great point to test. If present, check enable signal. If good, replace U6960.
 * }

Charger or Battery is connected:
PPBUS_G3H

PP3V3_G3H_RTC

PP3V3_G3H

PP3v3_G3H_PMU_VINRTC_R

PP1V8_SLPS2R

Early T2 Initialization:
PMU_CLK32K_SOC

PP1V8_AWAKE

PP1V8_SLPS2R_PMUGPIO

PP1V1_SLPS2R

PP0V8_SLPS2R

PP0V82_SLPDDR

PP3V3_AWAKE

PPVDDCPUSRAM_AWAKE

PP0V9_SLPDDR

PP1V1_SLPDDR_SOCFET_EN

PP1V1_SLPDDR H9M_24MHz_CLK

PP1V2_AWAKE PPVDDCPU_AWAKE

PMU_SYS_ALIVE

PMU_ACTIVE_READY

PMU_COLD_RESET_L

T2 Loads ROM (U4770)
PMU_PVDDMAIN_EN

P3V3MAIN_PGOOD

PP3V_G3H_RTC

PMU_CLK32K_PCH

PCH_RTC_RESET_L

P5VG3S_EN

PP5V_G3S

P3V3G3S_EN

PP3V3_G3S

P1V8G3S_EN

PP1V8_G3S

P5VG3S_PGOOD

PMU_CLK32K_WLANBT

T2 begins communication with SSD PMICs (U9000/U9500) to enable SSD power
SSD_PMU_RESET_L

PP1v8_SSD0/1
PP0V9_SSD0/1

SSD0/1_VR_2V5_EN

PP2V5_NAND_SSD0/1

SSD0_OCARINA_WP_L

SSD0_OCARINA_PFN SSD0_PCARINA_RESET_L

Further U9000 Communication to enable SSD Power
PP1v8_SSD0/1

PP0V9_SSD0/1

SSD0_PMIC_DISCHARGE_EN

SSD0/1_VR_2V5_EN

PP2V5_NAND_SSD0/1

SSD0/1_VR_P2V5_PGOOD

SSD0/1_PMIC_RESET_L

T2 Begins Power Button Monitoring for power on signal
PMU_ONOFF_L

PP3V3_S5

PP1V8_S5

PPVPCORE_S5

PP1V_PRIM

SMC_RSMRST_L

PM_RSMRST_L

T2 waits for eSPI_RESET_L signal (After power on signal is given)
PCH_PWRBTN_L

PP1V8_S3

PVDDQ_EN

PP1V2_S3

PVDDQ_PGOOD

PP1V_S3

Final power stage enable (Enables CPU CORE voltage and final PGOOD signals)
PVCCPLLOC_EN

PP1V2_S0SW

PP1V_S0SW

PVCCIO_EN

PVCCIO

PVCCIO_PGOOD

ALL_SYS_PWRGD

CPU_VR_READY

PM_SYSRST_L

PM_PCH_PWROK

PM_PCH_SYS_PWROK