For those of you on custom ROMs and you don’t want to unroot back to Gingerbread to take the official T-Mobile ICS update, here’s how to easily unroot/unbrick your Galaxy S2 SGH-T989 back to official ICS.
*Note – This method requires a Windows computer. Sorry Heimdall does not support T-Mobile Galaxy S2 yet.
Step 1. Connect a microUSB cable from your T-Mobile Galaxy S2 SGH-T989 to your computer. Then hold down Volume Up, Volume Down, and Power button together for about 10 seconds.
Step 2. When your phone resets, you will feel a small vibration, let go of the Power button but hold the rest of the buttons down.
Step 3. When you see the warning screen, hit Volume Up button to enter ODIN download mode.
Step 4. You should see Downloading… sign like below.
Step 5. Download the file SGH-T989_UVLE1_ICS.zip and unzip, you should find 3 files.