Found this guide on Android Forums:
If followed correctly, this a bulletproof method (reposted from our work at Rootzwiki) of returning any image to a true 5.5.886 stock and then applying the OTA update.
Commands/Screenshots
Necessary Resources
- Moto-Fastboot Commands
- Root Commands
- Boot Mod Commands
- ***All the files you must have in one folder - Full Package from below***
Optional Resources
- Motorola Drivers v5.4.0 (32-bit) or Motorola Drivers v5.4.0 (64-bit)
- 5.5.886 Radios (radio.zip)
- Full Package of All Other Files You Will Need: Link 1 or Link 2 or Link 3
Fastboot Mode
- 5.5.886 Boot Mod
- 5.5.886 FXZ Restore File
- Motorola Fastboot
- Root and Forever Root Files
- ADB-Fastboot Files
- 5.5.893 OTA Update
- RSDLite v5.6
Recovery Mode
- Make sure the phone is off
- Hold down the Volume Down + Volume Up buttons and press the Power button
- When the choices appears, press Volume Down twice, till "AP Fastboot" is selected
- Press Volume Up to select
Step-by-step Process
- Make sure the phone is off
- Hold down the Volume Down + Volume Up buttons and press the Power button
- When the choices appears, press Volume Down once, till "Recovery" is selected
- Press Volume Up to select
- When the icon with the android and exclamation appear press both Volume Up and Volume Down at the same time to enter the recovery
- Download the 3 files under "Necessary Resources"
- Install the appropriate Motorola drivers for your operating system
- Place the radio.zip file on the root of your SD card (not internal storage)
- Unpack the full package of files to one folder on your computer
- Turn off your phone completely
- Start into Fastboot Mode (listed above)
- Connect your phone to your PC with the USB cable and let it install the drivers for your device
- After the drivers are done installing, open a command prompt in the folder where you unzipped the full package to
- Using the Moto-Fastboot Commands screenshot from above follow each one step by step until you are done
- When you have finished, disconnect your USB cable and press the Power button once to turn it off
- Start into Recovery Mode (listed above)
- Highlight "wipe cache partition" and press the Power button to select it
- When it has completed, pull the battery out of your phone and then put it back in
- Start into Recovery Mode again
- Highlight "apply update from sdcard" and press the Power button to select it
- Highlight the "radio.zip" file on your SD card and press the Power button to select it
- When it has completed, highlight "reboot system now" and press the Power button to select it
- When the device reboots into the OS waited 1 minute for it to load everything in the background
- Follow the prompt but don't sign into anything, just get to the homescreen
- When at the homescreen, connect your USB cable and then from the pull down menu select "USB connection", then select "Charge Only" and hit OK
- Go into Settings -> Applications and enable Unknown Sources and hit OK
- Go into Development and enable USB Debugging and hit OK
- Back out to Settings -> Battery & data manager -> Battery mode and select Performance mode
- Power off your phone and then power it back on normally
- Open a command prompt in the folder where you unzipped the full package to
- Using the Root Commands screenshot from above follow each one step by step until you are done
- Power off your phone and then power it back on normally
- Open a command prompt in the folder where you unzipped the full package to
- Using the Boot Mod Commands screenshot from above follow each one step by step until you are done
- ***When a Superuser prompt appears on your phone after the last command, quickly select Allow and make sure you do NOT reboot your phone***
- When it has finished, connect your phone to your 3G/4G or a WiFi connection
- Go into Settings -> About phone and select System updates
- When the prompt comes up, press Setup
- Place a check in "I agree to the Motorola Terms of Service" and then press Next
- When the update prompt comes up, press Download
- Wait for the update to download
- When the update prompt comes up, press Install Now
- Let update reboot to recovery and install itself
- ***Your phone may appear as if it is completely off for a little while but leave it be it will turn itself on and continue***
- Let the update finish and then it will reboot back into your system
- Congratulations! You now have the official 5.5.893 update installed and are back on the official OTA path and forever rooted
Credit to all developers of the zergRush exploit, to realbbb (from Rootswiki) for discovering the Boot Mod, and anyone else who participated in making this all possible.