Yosemite and El Capitan USB crash kills keyboard and trackpad

Solution 1:

The start up sequence is kind of hard to emulate other than actually power cycling the computer.

I don't have a good answer since his failure is extremely low level, but here are the things I would do to troubleshoot and isolate things before considering a total reinstallation of the OS:

• run sysdiagnose script each time a failure happens to capture the logs and also gain a sense of how often this happens.
• verify that plugging in the USB keyboard does not kick start the system properly for internal or external keyboard function
• log out the user using kill -9 -1 or via remote screen sharing

My guess is the logs will show USB errors indicating a hardware fault, but that would need a look at your specific logs. It's not clear why you are manually loading the kext so perhaps I'm missing some information?