Flash radio on Nexus 4

So you've upgraded your Nexus 4 to a version of Android past 4.2.1 and want your LTE functionality back? No problem.

You'll need to re-flash your LTE radio. However, 4.2.2 introduced a few other things, such as increased security on adb. So before we get started, you'll need to update your android sdk. You can do this from the gui via

$ cd /path/to/your-android-sdk
$ android

Or simply download the latest .zip from google, extract the necessary files and folders from the archive (notably platform-tools) and overwrite your previous folders.

All done? Let's get started. First, head on over to XDA-Developers and download the stock radio for the Nexus 4. This should be the 0.33 link in the list.

Once you've downloaded the radio image, copy it to your phone's sdcard via USB or adb, as you prefer. Power down your phone, then hold the volume down button while you power the phone back up. Press down twice to select recovery, then press power to enter recovery mode. Once in recovery, choose "install zip from sdcard". Browse to the file you just copied to the phone, and install it. When finished, choose "reboot system now".

Once your phone is back up and running, be sure to select the correct APN in Settings->More...->Mobile Networks, and use the dialer to enter *#*#4636#*#* to switch from "WDCMA Preferred" to "GSM/LTE Auto" to get your 4G functionality back.