When HTC's yet-unreleased official over-the-air Ice Cream Sandwich update (3.32.401.3) for the HTC Sensation was leaked, XDA Developers member rmk40 immediately went to work.

The leak was, unfortunately, not packaged as a directly flashable ROM, but rmk40 was able to cook up a version flashable via ClockworkMod Recovery.

But, there's more.  The leaked update, being official from HTC, bears not just stock Android 4.0.3 Ice Cream but also stock HTC Sense 3.6.  rmk40′s flashable version is also pre-rooted, so if you upgrade your HTC Sensation to this leaked update, you won't need to root it again.

Follow our step-by-step guide on how to manually update your HTC Sensation to stock Android 4.0.3 Ice Cream Sandwich and stock HTC Sense 3.6.

Requirements

• A rooted HTC Sensation with ClockworkMod Recovery installed. Check out this rooting guide for your mobile phone.
• HTC USB drivers for your phone must be installed on your Windows computer.  Install HTC Sync to also install the drivers.
• To keep your phone alive all throughout the flashing procedure, you will need to maintain a battery of 70% or more prior to installing the ROM.
• Safely store all your mobile phone data and files by creating a backup.
• Temporarily disable system tools such as firewall programs and antivirus software to ensure a smooth installation process.
• Enable USB debugging on your phone by going to Settings > Applications > Development > USB debugging.

Important Reminders

• These flashing instructions are for the HTC Sensation only.  Don't try these on another phone.
• Update your phone at your own risk. We will not be liable for any damage that you cause to your phone.

Instructions

1. Download the ADB and Fastboot (ADB_Fastboot_Windows.zip) package from here.
2. Unpack ADB_Fastboot_Windows.zip into C:ADB_Fastboot_Windows
3. Connect your phone to your computer via USB cable.
4. Open a command prompt window on your computer.
5. Enter the following commands at the command prompt:
   • cd C:ADB_Fastboot_Windows
   • adb reboot bootloader
   • fastboot getvar cid
   • fastboot getvar mid
6. Take note of the CID and MID (model ID) values.
7. Reboot your phone into normal mode by entering the following command at the command prompt:
   • fastboot reboot
8. If the fastboot method doesn't work for you, download and install CID Getter on your phone.  Run the app.  The CID will be shown at the top of the screen.  For the MID, scroll down to style=”font-style: italic;”>[ro.mid].
9. Open this post on XDA Developers and look for your CID and MID on the list.
10. Download the latest firmware version for your CID and MID.  The latest version is 3.32 Unlocked.  Make sure you download the right file for your specific CID and MID.
11. The file you will be downloading is named PG58IMG.zip.  Save the file to your computer and don't extract it.
12. Download the leaked Ice Cream Sandwich update ROM from here.  Save the file to your computer but don't extract it.
13. Copy the two downloaded ZIP files into the root of your phone's internal SD card (/sdcard).
14. Disconnect your phone from your computer.
15. Turn off your phone.  Don't touch it for about one minute.
16. Press and hold both the Volume Down and Power buttons.  This will power on the phone in HBOOT.
17. Press the Volume Down button to highlight “recovery.”
18. Press the Power button to enter recovery mode.  When in recovery mode, use the Volume keys to scroll items and the Power key to select items.
19. Go to Backup and Restore > Backup and create a Nandroid backup of your ROM.  This is not optional.  Do it now before you proceed.
20. Select “wipe data/factory reset” on the recovery menu.  Confirm the operation on the next screen.
21. Select “install zip from sdcard.”
22. Select “choose zip from sdcard.”
23. Locate the ICS update file that you copied to the phone earlier (rmk-pyramid-stock_ics_3.32.401.3-v1.zip).  Select the file.
24. Confirm that you want to flash the ROM.
25. Select “go back” to return to main menu.
26. Power off the phone.  DO NOT reboot it.  Just power it down.
27. Leave the phone untouched for about 1 minute.
28. Hold down both the Volume Down and Power buttons.  Keep the Volume Down key pressed until the bootloader menu appears.
29. Use the Volume keys to highlight “fastboot.”  Tap the Power button to select it.
30. Your phone will automatically attempt to detect any update file (PG58IMG.zip).
31. When prompted to apply the update, select “Yes”.  Wait a bit for the update to finish.
32. Reboot your phone.
33. If your phone does not reboot properly, as has been the case of some users who did this update, try repeating the process from step 26 until the end.

Congratulations!  Your HTC Sensation is now running on official Android 4.0.3 Ice Cream Sandwich and HTC Sense 3.6 via the leaked, pre-rooted OTA update version 3.32.401.3.