How to get my Intel Wireless 3165 to connect on 15.04?

I had this same problem but figured it out. The best way to see if this was your issue is to run this script:

wget -N -t 5 -T 10 https://github.com/UbuntuForums/wireless-info/raw/master/wireless-info
chmod +x wireless-info
./wireless-info

You'll find the output in the /root directory. Toward the bottom of the output, you may see some dmesg errors that say that it has attempted to load the right iwlwifi drivers but ultimately says "no suitable firmware found!"

To fix this problem:

1. Check the Linux kernel you are using

   uname -r
   

   Even if you've installed Ubuntu 15.04, it's still using the 3.19 Kernel.

2. Right now, Intel is only supporting the 3165 hardware with firmware for 4.1+, but I couldn't get it to work until I upgraded to 4.2. It's easiest by using wget to get the right version for your hardware, and for whatever kernel you want to use. I used the most recent version on kernel.org. Use wget to get them:

   wget http://kernel.ubuntu.com/~kernel-ppa/mainline/v4.2-rc8-unstable/linux-image-4.2.0-040200rc8-generic_4.2.0-040200rc8.201508240030_amd64.deb http://kernel.ubuntu.com/~kernel-ppa/mainline/v4.2-rc8-unstable/linux-headers-4.2.0-040200rc8_4.2.0-040200rc8.201508240030_all.deb http://kernel.ubuntu.com/~kernel-ppa/mainline/v4.2-rc8-unstable/linux-headers-4.2.0-040200rc8-generic_4.2.0-040200rc8.201508240030_amd64.deb
   

   And then issue the following command:

   sudo dpkg -i *.deb
   

   Reboot and you should now see the correct kernel:

   sudo uname -r
   

   Update and upgrade, and you're all set:

   sudo apt-get update
   sudo apt-get upgrade
   

   Suddenly, wireless. And this time, you can actually connect to it. :D

   Some last minute clean up, regenerating the grub menu and removing the previous kernel:

   sudo update-grub
   sudo apt-get autoremove
   

BAM! You're done.