(adsbygoogle = window.adsbygoogle || []).push({}); IMPORTANT: YOUR BOOTLOADER MUST BE UNLOCKED AND YOUR NEXUS 5 MUST BE ROOTED!

This is for people who have errors installing a certain ROM on their Nexus 5 like the new CyanogenMod 12. This is most likely due to an outdated bootloader. You're probably on the HHZ11k bootloader, but it is best to go into fastboot and check what bootloader you're using.

This method works for any version of a bootloader, but it is recommended that you upgrade to the HHZ12d bootloader as it is the latest version.

Step 1, get into fastboot
Turn off your phone, then hold the power button + volume down to enter fastboot. A black screen should pop up with some content on it (Start, Recovery, Restart Bootloader, Power Off)

Step 2, plug your phone into your computer/laptop
Plug your Nexus 5 into your computer/laptop using a micro-USB cable. You must do this to continue the process.

Step 3, get the files
You must get these files:
Fastboot.zip: You must login or register to view this content.
HHZ12d bootloader (RECOMMENDED): You must login or register to view this content.
Then unzip the Fastboot.zip and add the bootloader img file into the Bootloader folder.

Step 4, command prompt
Open a command prompt for Windows or terminal for Mac/Linux.

Step 5, add commands
For Windows, type:
cd Downloads
cd fastboot
fastboot flash bootloader bootloader-hammerhead-hhz12d.img

For Linux, type:
cd Downloads
cd fastboot
chmod 755 *
./fastboot-linux flash bootloader bootloader-hammerhead-hhz12d.img

For Mac, type:
cd Downloads
cd fastboot
chmod 755 *
./fastboot-mac flash bootloader bootloader-hammerhead-hhz12d.img

The results should be successful.

Step 6, double-check
Power off your phone, then go back to fastboot again.
It should say "BOOTLOADER VERSION - HHZ12d"

And that's it folks! Hope this helped.

If you want a different version of the bootloader (not recommended), just search it online and download another one and use the same steps, except you don't use the HHZ12d bootloader img file.