USB port not working

Thanks man, will try definitely.

No need! You've got a short!

From the sounds of it you go a bad I/O board as the shield should be firmly mounted and your cable maybe damaged as well from the high current load being pushed through it.

The shield is a Faraday Cage - EMI shield to protect sensitive components. Just like a paper cup which can hold water it can also float on water! The emissive signal can be inside or outside of the container like the cup with water. The EMI designer decides which way the shield is to be used. It needs to be grounded the chassis which in its self is a Faraday cage as well as its a full metal enclosure.

@danj Thanks for replying Dan!

So the EMI shield should protect it from interference and only works when properly grounded? Shouldn't explain the high current right? Your advice is to replace the flex cable and I/O-board? And maybe order the datacable as well, and if not needed return that?

Haven't got the Macbook with me right now as it's from a friend, but i'll check the Datacable on the Logicboard side aswell, as it does work for USB, just not for SD card reader. The SD card reader get's recognized properly, just doesn't mount anything or detect a SD card. SD card works in a MBA 2014. Thanks again!

You should only need the I/O board and the I/O board cable. The data cable is for the video signal to the HDMI port.

What is ground? What you are walking on? What if you are in the ISS floating over head?

The words meaning in this context implies electrial ground. The chassis of the TV which is covered by a plastic & glass box so you can't touch it! A light fixture in the ceiling again maybe the pull chain to turn it on, Or, the metal case of your computer. Check out the link I posted on "Faraday Cage" if you want more.