Chosen Solution
I just did a clean install of El Capitan from a usb drive and erased the SSD of my MacBook Pro. When I go to System Preferences nothing appears in the Network settings. In System Information I noticed that there are a lot of hardware parts where it says: “No information found.” Or “No hardware was found.” This goes for quite some parts like Thunderbolt, PCI, Card Reader and Bluetooth. It seems to me like drivers are missing. Is it possible that I might have deleted them when I erased the SSD? And if so, is it possible to install the drivers from Apple? Where can I find those? Thanks in advance!
Shutdown your MacBook/Pro. Connect the power adapter to your Mac. On the MacBook/Pro’s keyboard, hold down the Shift+Control+Option keys and the Power button at the same time. Release all keys and the power button simultaneously. Boot your Mac as usual. Update (01/03/2018) or Cmd + option +p+R
You have multiple hardware issues here which cover different areas within the system. I’m still suspecting some level of liquid spill which has seeped onto the main logic board. But as you stated that is not the case then we have three different things happened at once! Lets start with the keyboard & trackpad: This series routes both ribbon cables under the battery so if either cable is damaged you would need to replace the uppercase. Here’s the IFIXIT guide: MacBook Pro 15" Retina Display Early 2013 Upper Case Assembly Replacement This also resolves a swelled battery issue as well. As far as the screen backlight: There are two fuses on the back side of the logic board which may have burnt here’s an image of there location marked in Red:
I would test these and also do a full inspection making sure there is no corrosion or other damage visible around this chip. Here’s the IFIXIT guide you’ll need to follow: MacBook Pro 15" Retina Display Early 2013 Logic Board Replacement
