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MacBook Pro 16" A2485 M1 Max (2021): No internal display - external works fine

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  • forkus
    Member
    • Feb 2026
    • 11
    • Spain
    #1

    MacBook Pro 16" A2485 M1 Max (2021): No internal display - external works fine

    Hi everyone,

    I'm troubleshooting a MacBook Pro 16" A2485 M1 Max (Late 2021, board 820-02382) with a completely dead internal display. No image, no backlight. External monitor works perfectly via USB-C or HDMI.

    Symptoms:
    • Internal display detected in System Information (shows as "Built-in Liquid Retina XDR Display")
    • No image (no 100% sure), no backlight (100%)
    ​Apple Diagnostics codes: VFD001

    Measurements taken:
    • PPBUS_AON_LUXE: 12V (schematic shows 13.1V — running without battery on charger only)
    • PPVOUT_LUXE (CP834): 0V
    • No short to ground on PPVOUT_LUXE
    What is the fastest way to determine whether the fault is on the motherboard side vs inside the display assembly?
    1. Is my understanding correct that the absence of PPVOUT_LUXE does not necessarily indicate a motherboard fault, it could also be a protective response to a fault inside the display assembly?
    2. Is there a reliable way to confirm whether the eDP signal is also absent without an oscilloscope? I attempted to see an image with a flashlight but I'm not 100% certain. It appears there is no image either, not just backlight but I want to confirm this before drawing conclusions.
    ​​Thanks!
    Tags: None
    • forkus
      Member
      • Feb 2026
      • 11
      • Spain
      #2
      Nevermind. It's flexgate issue again.

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