If you've been running a stock Nexus and have been patiently waiting for the 4.0.4 update, your wait is over. Thanks to our friends over at XDA and Droid-Life, we now have the 4.0.4 IMM76K update available for manual installation.
Instructions [Rooted users]:
1. First, you have to be stock and rooted, running 4.0.2 (ICL53F).
2. You also have to be running the stock radios ek02 and ek05(found here).
3. Download the update file to your internal storage.
4. Rename to update.zip if you’d like.
5. Reboot into recovery and make a backup just to be safe.
6. Select “install zip from sdcard” and then “choose” and find the file.
7. Apply it and reboot. Enjoy 4.0.4 and hopefully a lot less bugs.
*Note – If you are running a custom ROM and do not have an ICL53F backup, you can return to stock by following this set of instructions.Remember that you don’t want to do the “fastboot oem lock” command though.
*Note 2 – If you are running the leaked 4.0.4 (IMM30B), it is looking like you will need to go back to ICL53F, unless someone can find a full blown IMM76F .zip or a .zip that takes you from IMM30B to it.
Instructions [Non-rooted users]:
1. Non-roots, you can use the Galaxy Nexus Toolkit from XDA to flash a temporary custom recovery.
2. After doing that, you can flash the file and update. Upon rebooting, you will have stock recovery back.
3. So it seems like you are “rooting” but you aren’t. After updating, you will be back to fully stock.
4. Links: Instructions | Toolkit
Source: Galaxy Nexus Forum via Droid-Life via XDA