Encountered a potentially troubling situation recently when I wasn’t able to obtain a wired Ethernet connection from my MacBook Pro, while wifi worked fine. For security and stability reasons, I rely on my wired Internet connection. Fearing a major repair bill, I found the simple fix after failing to get the desired result from following standard troubleshooting techniques suggested on blog posts.
The internal drive of my laptop is dual-boot, and I also have an external drive that can start up in either macOS 10.12 or 10.14. Because I have multiple OSes on different drives, I tried them all. In each case, the Ethernet setting in System Preferences showed a self-assigned IP address. In addition, my PinePhone also could not access the Internet using its special Ethernet adapter.
What to Do?
I reset the NVRAM/PRAM (Parameter RAM) by holding down the Command, Option, P, and R keys simultaneously while booting. Zip. Nada. No change whatsoever.
Next, I reset the SMC (system management controller) chip that regulates temperature, power management, and battery performance on Intel-based Macs. Although my pre-2015 laptop has a removable battery, I figured I could reset its SMC by not taking the time to remove the battery and, instead, follow the steps used for MacBooks with non-removable batteries.
• Shut down your Mac. Press and hold Shift, Control, and Option on the left side of the keyboard.
• Now press and hold the Power button (or Touch ID button) as well.
• Hold all the keys down for 10 seconds.
• Release all the keys and turn on your MacBook.
Nice try, but nothing to show for my effort.
Then, I read a blog post that said that the type of Ethernet connection problem I was having may be caused by an Apple kernel extension file called AppleKextExcludeList.kext that is located in the System folder. The problematic kernel extension is version 3.28.1 that should be updated to version 3.28.2 in order to correct this problem.
From this point, I stumbled upon another web page that described an easy way to determine the version of AppleKextExcludeList.kext that is installed on my Mac.
• While holding down the “option” key, click on the “System Information” from the Apple menu in the menu bar.
• Open the “software” section and then click on the “installation” section.
• Then sort the information by clicking on the “software name” column.
• Proceed with searching the update “Incompatible Kernel Extension Configuration Data” on the list.
When I ran this procedure from the Apple Menu, I learned that I already had version 3.28.2 installed, so no updating of the kernel extension was necessary.
The Simple Solution
Whenever I consult customers about a network connection problem such as this, the most common advice that I give them is to disconnect and reboot the hardware. I left the modem alone and chose, instead, to temporarily disconnect the power cord to the router — keeping it unpowered for several minutes before powering it back up again and waiting for the signal to sync back up.
BINGO! I had just restored the wired connection to my MacBook Pro! Case closed.