Mac OS X 10.5.6: black display on MacBook Pros after updating

Previously, MacFixIt reported on a problem experienced by many MacBook Pro owners in which systems were not starting up properly after installing Mac OS X 10.5.6. After installing, the system would reboot twice as expected and then the screen would not light up, resulting in basically a useless laptop.

This problem was initially suspected to be caused by a faulty firmware update in the 10.5.6 package, but it turns out users who have been affected by this problem have not updated their MacBook Pros to the latest EFI firmware. Mac OS X 10.5.6 installed some additional firmware updates which were incompatible with the older EFI firmware, and this resulted in the faulty video.

The latest EFI firmware (v1.5.1) is available for download here.

In order to fix this problem, users should first ensure their firmware is the older version. This can be done after users establish visibility to the Finder and Desktop by either screen sharing or connecting an external display (described below).

To check the firmware version, open "System Profiler" and with the "Hardware" section highlighted, check the "Boot ROM Version". If the string of letters and numbers is NEITHER "MBP21.00A5.B08" or "MBP31.0070.B07", users will have to update their firmware.

There are two ways to do this: through screen sharing, or though external displays. NOTE: Updating firmware can harm the computer if it is not done properly, so be sure to follow all on-screen instructions in the updater utility, and ensure the computer is attached to an external power source.

Fixes

Use screen sharing MacFixIt previously suggested that users with Screen Sharing enabled use this to connect to their computers and reapply the 10.5.6 combo updater. This is again the recommendation, but users should apply the firmware update this way instead.

Use external display and keyboard The MacBook Pro will function with an external display as the main monitor if users attach it to one along with an external keyboard (and mouse), and then close the lid. The computer will automatically detect the display, and then stay awake with the lid closed if a keyboard is attached. In this setup, the computer will be fully usable, and users can download and apply the EFI firmware update.

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