Complete Solution for Brightness Adjustment Failure on M1 MacBook Air After Image Restoration/Downgrade (Including DFU Reinstal)

1. Core Cause of the Issue (Newly Added)

Brightness failure essentially stems from incompatibility between macOS version and firmware version. Here, “firmware” refers to the device’s low-level control program (not traditional BIOS). The display driver can only load normally when the system version and firmware version are strictly matched.

Steps to Verify Version Compatibility:

  1. Click the Apple menu in the top-left corner → “About This Mac” → “System Report”

  2. Under the “Hardware” section on the left, check:

  • System Firmware Version (e.g., 7459.141.1 as mentioned in the reference document)

  • Operating System Version (must match the firmware; e.g., Firmware 7459.141.1 matches macOS 12.5.1)

  1. If the two versions do not match, DFU-mode reinstallation of a compatible system is required.

2. Quick Temporary Fixes (Original Content Retained with Supplementary Notes)

1. Keyboard Function Key Check

  • Open “System Settings” → “Keyboard”

  • Ensure “Use F1, F2, etc. keys as standard function keys” is unchecked

  • Test the Fn+F1 (decrease brightness) / Fn+F2 (increase brightness) key combinations

Note: Only applicable when versions are matched but the driver fails to load temporarily.

2. Lid Closure & Wake Reset

  1. Fully shut down the Mac (press and hold the Power button for 10 seconds)

  2. Immediately close the lid after pressing the Power button to turn on the device; wait 10 seconds

  3. Open the lid to wake the device—brightness adjustment usually resumes normal function

Principle: Triggers a reload of the display driver, applicable to systems with driver loading bugs (e.g., macOS 13.7).

3. System-Level Fixes (Original Content Retained with Supplementary Firmware Check)

1. NVRAM Reset (M1-Specific Steps)

  1. After shutting down, press and hold the Power button until startup options appear

  2. Press and hold Option+Command+P+R simultaneously for 20 seconds

  3. Release the keys and start the device normally; re-verify firmware and system versions after restart.

2. Terminal Command Fix (Core Solution)

Open “Terminal” and execute the following commands (administrator privileges required):

\# 1. Reset display driver cache

sudo kextcache -i /

\# 2. Repair power management parameters

sudo pmset -u

\# 3. Disable conflicting auto-brightness function

sudo defaults write /Library/Preferences/com.apple.iokit.AmbientLightSensor "Automatic Display Enabled" -bool false

\# 4. Restart WindowServer

sudo killall -HUP WindowServer

Test brightness adjustment immediately after execution. If it fails, restart the device. If the issue persists, DFU-mode reinstallation is required.

3. Safe Mode Verification

  1. Press and hold the Power button after startup until startup options appear

  2. Hold the Shift key and click “Continue in Safe Mode”

  3. If brightness works normally in Safe Mode, third-party software conflict is the cause—uninstall recently installed apps.

4. Firmware-Matched DFU Reinstallation (Newly Added, Core Content from Reference Document)

1. Preparations

Tool/Device Requirements
USB Cable Original cable preferred; non-original cables must support data transfer (avoid charge-only cables)
Secondary Computer Option 1: Mac (must be upgraded to macOS 14.5+); Option 2: Windows (requires VMware virtual machine); Option 3: Linux (Fedora 41+)
System Firmware (ipsw) Download macOS 12.5.1 (Build 21G83) matching the device. Reason: No substantial updates in 12.6+, and 12.5.1 offers optimal compatibility
Download Link https://ipsw.me/download/MacBookAir10,1/21G83 (select the correct device identifier)

2. Steps to Enter DFU Mode

  1. Fully shut down the M1 Mac and disconnect all peripherals (except the USB cable)

  2. Press and hold the Power button without releasing it, then connect to the secondary computer via USB cable

  3. Keep holding the Power button for 10 seconds, release for 1 second, then hold the Power button again for 5 seconds (the device screen remains black, indicating successful DFU entry).

3. Reinstallation Operations for Different Secondary Devices

Option 1: Using a macOS 14.5+ Computer

  1. Open “Apple Configurator 2” (available for download from the App Store)

  2. After the DFU device is detected, hold the “Option” key and click “Restore”

  3. Select the downloaded 12.5.1 ipsw file in the pop-up window; wait for reinstallation to complete (approximately 15-20 minutes).

Option 2: Using Windows (VMware Virtual Machine)

  1. Install macOS 14.5+ in VMware and set up “VMware Tools” (ensure USB passthrough is enabled)

  2. Drag the 12.5.1 ipsw file into the virtual machine and follow Step 1 for operation (ensure the virtual machine detects the DFU device)

  3. Keep the virtual machine awake during reinstallation to avoid USB connection interruption.

Option 3: Using Fedora 41 Linux
  1. Open Terminal and install the idevicerestore tool:
sudo dnf install idevicerestore -y
  1. Execute the reinstallation command (replace <ipsw-path> with the actual file path):
idevicerestore -d -f \<ipsw-path>.ipsw
  1. Wait for the command to complete; the device will restart automatically to finish activation.

5. Advanced Solutions (Original Content Optimized with Supplementary Version Selection)

1. Two-Way System Version Selection

  • Solution A (Permanent Fix via Upgrade): If the current system is macOS 12/13, back up data and upgrade to macOS 14 (Sonoma) or 15 to fix underlying driver bugs

  • Solution B (Downgrade for Compatibility): If macOS 12 must be retained, use version 12.5.1 (verified as optimal in the reference document) and avoid 12.6+.

2. Recreate Recovery Image

If the image itself is faulty:

  1. Download the official recovery firmware for the corresponding device (M1 MacBook Air requires matching the “MacBookAir10,1” model)

  2. Use “Disk Utility” → “Restore” → “Restore from Disk Image” and select the correct ipsw file

  3. Erase the disk and perform a clean system recovery (back up data to avoid residual files from the old system).

6. Hardware-Related Troubleshooting (Original Content Retained with Supplementary Firmware Check)

1. Sensor Detection

Execute the following command in Terminal to check the ambient light sensor status:

system\_profiler spdisplaysdata type | grep -i "Ambient"
  • If no result is output, contact after-sales support to inspect the sensor hardware.

2. Dual Check for Firmware & System Versions

\# Check system firmware version

system\_profiler SPHardwareDataType | grep "System Firmware Version"

\# Check macOS version

sw\_vers -productVersion
  • If versions do not match (e.g., Firmware 7459.141.1 with System 12.6), reinstall macOS 12.5.1 via DFU.

3. TCON Firmware Check

systeminformation -json | grep TCON
  • If the firmware version is lower than v2.3.1, schedule an appointment with an Apple Store to upgrade the backlight control chip firmware.

7. Key Notes (Newly Added, Key Reminders from Reference Document)

  1. Disable System Updates: After reinstalling macOS 12.5.1 via DFU, disable automatic updates in “System Settings” → “General” → “Software Update” to prevent upgrading to 12.6+ (which may reintroduce brightness issues)

  2. ipsw Version Selection: Must use 12.5.1 (21G83). The reference document verifies that 12.6+ has no essential updates and suffers from brightness driver compatibility issues

  3. Secondary Computer Requirements: Windows requires a virtual machine (direct tools have compatibility issues); Linux prefers Fedora 41 (idevicerestore in other distributions may be outdated).

8. Official Support Channels (Original Content Retained)

  1. Remote Diagnosis: Initiate a remote session via the “Apple Support” app

  2. Hardware Inspection: Bring the device to an Apple Authorized Service Provider, focusing on inspecting the display cable and backlight control module

Note: Unauthorized repairs may void the warranty.