Google released the factory image for 5.0.2 for the Nexus 7 2012 Wifi, a few days ago.
And now, the OTA zip file for the update is now available for download.
Disclaimer: AndroidPure is not responsible for any damage you incur during the process.
NOTE: The following procedure is for updating the Nexus 7 2012 Wifi from Android 5.0 LRX21P to Android 5.0.2 LRX22G.
1. Download the 13 MB Android 5.0.2 OTA update file from Google, and save it on your PC. The filename is a6645eee89af34f58db74f6a1ad93fe400fcfc7b.signed-nakasi-LRX22G-from-LRX21P.a6645eee.zip
(MD 5: 12462A8DDB3CBC06E86D715D40C129A4)
You can rename the file to whatever you want.
2. Now open a command prompt with admin rights, on your PC.
3. Connect the Nexus 7 to your PC using the USB cable.
4. Type the following command in the command prompt window, and press enter.
adb reboot bootloader
5. The tablet should reboot to the bootloader, now press the Volume Up key to highlight recovery mode. Press the power button.
6. You should see an Android lying on its back, with a red exclamation mark. Press Volume Up and Power simultaneously and release both together.
7. Your tablet is now in the recovery mode. Use Volume Up or Down, to highlight the Update from ADB option, and press the Power button.
8. Now enter the following command in the command prompt window, and press enter.
9. Type the following command, replacing the [OTA Filename] with whatever you renamed the file, and press enter.
adb sideload [OTA Filename].zip
For example, I did not rename it and I saved the file to D:, so I just used Ctrl+C/Ctrl+V to paste the whole filename and location like this:
adb sideload D:a6645eee89af34f58db74f6a1ad93fe400fcfc7b.signed-nakasi-LRX22G-from-LRX21P.a6645eee.zip
10. Wait for the process to complete. You will see a message which reads “Total Xfer”.
11. Reboot the device to complete the update process. It will take quite a while for the device to boot the first time, as it will be rebuilding the cache.
You need ADB 1.0.32 or newer to sideload to the device. Else, you may get an error like Protocol Fault (No status). You can use the latest version of Minimal ADB version 1.2 (or above)to sideload the update.
If you wish to update from KitKat to Lollipop 5.0.2, you can flash the factory image by following our tutorial here.
credits for OTA url: AndroidPolice