A1502 2015-2016 13” MacBook Pro Retina

Bad trackpad cable. This dies all the time.

On this year/model with 820-4924 board:

1. Keyboard signal goes to logic board.
2. Keyboard signal goes from logic board to trackpad.
3. Keyboard/trackpad signal is turned into a SPI or USB signal ON THE TRACKPAD, and then goes straight to the CPU from the trackpad cable.

The trackpad cable going bad will stop the keyboard and the trackpad from working. However, the keyboard power button will still function since this works separately.

If liquid damage, unplug everything, clean both sides of board, and test again.

U7100 ISL6259 bad, shorted current sense resistors R7121 and R7122 to ground through the U7100.

Most likely multiple issues are causing this. Can be cause by corrosion at clock chip, CPU Vcore and SMC.

Example: https://www.youtube.com/watch?v=lOwnVnVIc8w (corrosion at CPU Vcore, clock chip, SMC, capacitor and other components)

• PM_SLP_S4_L missing for random reason, thoroughly inspect clock chip, tiny specks of corrosion next to it can kill it. Sometimes shotgun replacement of the chip is a clean solution.
• CHGR_DCIN_D_R shorted to ground. [1]
• Bad right I/O board. Unplug it, see if it works (short on 3.3 V or 5 V rail on the I/O board can cause this problem).

Cause:

• PP5V_S0 shorted to ground via bad C6412 or C6432 capacitor, also PP5V_S3 will read shorted as it is connected to PP5V_S0

Fixed by replacing C6412 or C6432 capacitor. [2]

Cause:

• Spillage
• Corrosion on keyboard backlight connector
• Short to ground via keyboard backlight connector

Fixed by removing keyboard backlight connector. Replace with new keyboard backlight connector. See: [3]

• ADAPTER_SENSE not 3 V due to bad DC in board. 16–20 V on ADAPTER_SENSE means charger voltage is leaking into ADAPTER_SENSE, below 2 V means it is missing usually due to a bad DC In board.
• PP3V42_G3H missing
• SMC not working(if SMC is off, you will have 12.23 V on PPBUS_G3H instead of 12.56 V) because it is dead, not turning on(SMC_RESET_L low).
• Corrosion of the SMC's solder connections
• Keyboard bad, shorting PP3V42_G3H to ground or power button stuck on.
• Bad U7000
• Bad U7001
• Bad U7100 — indicators: PPBUS_G3H Below 4 V, board taking 40 mA, U7100 getting warm (check via thermal camera)

First, try a known good battery.

If it doesn't work, check PPBUS_G3H. If it is 12.23 V, the SMC is not communicating with the battery on its data line, either because the SMC is bad, or because the pullup resistors on the data line are bad. On rare occasion U7100 can pull down the data lines. There is a shared data line between the battery, SMC, and ISL6259 (U7100). If PPBUS_G3H is 12.56 V, then you probably have a bad battery.

Make sure the issue is no backlight, and not no image!

• Blown backlight fuse rarely if ever happens. This board has a current sensing circuit in place that keeps the backlight fuse from blowing if there is a short to ground on the backlight line.
• Short to ground on backlight output(if backlight fuse blown, check this).
• Bad screen/screen cable — if backlight voltage is 49–50 V, bad screen.
• USING WRONG SCREEN! If you use a 2012, or a 2013–2014 screen on a 2015–2016 A1502, it will not work properly. Backlight will only turn on once OS is booted, but not during early EFI boot process, unless you close the lid and open it again (or swipe a magnet over the hall sensor area)
• Data line between LCD and U7701 backlight driver is bad. Usually this should be 4.5 V–5 V. If it is lower, either the screen/screen cable is shorting it to ground(bad screen/screen cable), or a cap on the board or something is shorting it to ground, or the pullup resistor for it is bad. The screen NEEDS to talk to the LED backlight driver for it to turn on the backlight!
• If the screen is shorting the backlight to ground, you can fix the screen if the cap/connector on the screen is bad, it just sucks to do. But it is the only option since this screen is no longer available.

You can fix the screen if the cap/connector on the screen is bad, it just sucks to do. But it is the only option since this screen is no longer available.

• Bad screen cable
• Screen cable needs reseating (this fixes it a surprising amount of the time)
• Blown L8300
• Bad GPU inside the CPU.
• Bad U8300 causing partial short to ground on 5 V output causing screen to only receive around 3 V. Replace U8300 fixes this issue. Isolate whether the short is on the screen connector side or the U8300 side by removing the nearby inductor and measuring both sides of the pads where the inductor was.

When you find that 5 V is still missing on L8300 and LCD_PWR_EN is missing on U8300, do not chase since 99% of the time this turns out as a no fix (usually bad iGPU or MUX communication issues).

The machine running exceptionally slow with the fans spinning fast denotes a sensor issue. When a sensor is off, and it thinks the voltage/current is too high/low somewhere, or that the temperature is too high/low somewhere, it will clock the machine down and cause the fan to run at max speed. You have to use a tool that reads sensors like hwsensors, or boot into a Linux distribution to check your sensors, then chase down the circuit responsible for that sensor using the schematic/boardview. If all sensors are off, this usually points to an issue with the SMC or PP3V3_S5_AVREF_SMC.

• Bad trackpad can cause sensor issue. Water gets to the trackpad first in many occasions.
• Q5871 corroded, difficult to see without microscope, on edge of board.
• U5870 corroded, on edge of board next to fan where water comes in.

Corrosion around SMC chip and surrounding components, short on PP3V42_G3H, bad clock chip).

Example: https://www.youtube.com/watch?v=aMy3xLcH78g (Reflow of SMC, replaced surrounding components, jumper wire, used voltage injection to determine short, replacement of clock chip).

Corrosion at U5400 current sensing (R5400) circuit PP3V3_SO_HS_COMPUTING. This device makes power for the stages of CPU_VCORE. U5400 signals the SMC.

• Corrosion for U5400 was removed.
• Jumper wires were added to replace the faulty traces at U5400.
• U5400 and current sense resister restored.
• U7400 (Voltage regulator) chip was replaced and surrounding circuitry restored.
• Backlight circuitry and other areas cleaned up (corrosion).
• Example: https://www.youtube.com/watch?v=l6gqYTJPzbg

Corrosion at U1900 RTC (Real Time Clock) circuit

• U1900 and C1910 were removed
• Corrosion was removed
• U1900 and C1910 were restored.
• Example: https://www.youtube.com/watch?v=L8sc8ll7EaA