For those of you who want to unroot or unbrick your T-Mobile Galaxy S2 SGH-T989 back to Android 2.3.6 for whatever reason (maybe bricked or want to take it back for warranty), here’s how to do it.
UPDATE: There’s an unroot method to ICS, please see How to Unroot/Unbrick to ICS on T-Mobile Galaxy S2 SGH-T989!
*Note – You will need a Windows-based computer, does not work with Heimdall on Mac or Linux.
Step 1. Plug-in a micro-USB cable from your phone to Windows computer. Then hold down the Volume Up, Volume Down, and the Power button for about 10 seconds.
Step 2. When your phone resets, only let go of the Power button.
Step 3. Once you see the warning screen, hit the Volume Up button to enter Downloading Mode.
Step 4. Download ODIN and stock ROM below. Unzip both and you should get the ODIN program and ROM in tar file format.
Download Samsung Kies (if you don’t have it installed)
Run the Odin program and you will get the following screen. You should see a yellow-highlighted COM with a random number. If you don’t, make sure you have Samsung Kies installed and plugged your micro-USB cable straight to your computer’s USB ports, not a USB hub.
Step 5. Choose “PDA” and select the file “T989UVKL1_HOME_SGH-T989user_CL799405_REV00.tar” that you unzipped earlier and hit “Start”. Unrooting process will start and it should be done in about 10 minutes.
Step 6. When your phone reboots, you should find yourself on Android 2.3.6.
Step 7. You can go a step further and do a factory reset, go ahead and take the micro-USB cable out first then hold down Volume Up, Volume Down, and Power button together for about 10 seconds.
Step 8. Only let go of the Power button when your phone resets.
Step 9. Once in stock Android system recovery, choose “wipe data/factory reset” and hit the Home button.
Step 9. Reboot and your T-Mobile Galaxy S2 should be unrooted/unbricked back to Android 2.3.6 completely stock.
If official ICS Android 4.0.3 is out by the time you read this, you can still follow the same procedures then do a Software Update in Settings to unroot back to ICS.