CyanogenMod 9.1 (CM9.1) is a custom ROM based on Android 4.0.4 Ice Cream Sandwich. It provides fast and smooth performance along with stock Android 4.0.4 features and a lot of different customization options to further optimize and tweak the ROM. It's been in development for a while but it's now in stable form.

Thanks to members of the FreeXperia Project, CyanogenMod 9.1 is now available for the Sony Xperia S LT26i.  It is important to note though that this won't have the standard Sony-specific features, as it is a custom ROM.  And, being a work under active development, the ROM may still harbor bugs here and there, although most essential features are already functional and stable.

In this guide, you will learn how to flash CyanogenMod 9.1 for the Xperia S LT26i.

Warning

• The instructions in this guide are intended for use with the Sony Xperia S, model number LT26i. Applying these instructions on another device or model may produce undesired outcomes.
• The information in this guide is provided for instructional and educational purposes only. There is no guarantee that these instructions will work under your specific and unique circumstances.
• Use these instructions at your own risk. We shall not hold any responsibility or liability for whatever happens to you or your device arising from your use of the info in this guide.
• Read and understand the whole guide first before actually performing the instructions.
• Unlocking the bootloader voids your warranty, so make sure you have no problems with that before proceeding.

Requirements

• Sony Xperia S, model number LT26i with an unlocked bootloader
  • For help with unlocking the bootloader, see our guide on how to unlock the Xperia S’s bootloader.
• A Windows PC with ADB (Android Debug Bridge) installed
  • You can check our guide on how to setup and use ADB (Android Debug Bridge).
• Sony Xperia S USB drivers installed on the PC
• Your mobile phone's USB cable
• Download the following files to your computer:
  • ClockworkMod Recovery image file for Sony Xperia S (recovery-nozomi.img, 5.3 MB)
  • CyanogenMod 9.1 package for Sony Xperia S (FXP135-cm-9-20120824-UNOFFICIAL-nozomi.zip, 155.83 MB)
  • Google Apps package (gapps-ics-20120429-signed.zip, 49.6 MB)
  • Fastboot installer (fastboot-win32.zip, 279 KB)
• Make sure your device's battery still has at least 70% power. You don't want the device to shut down in the middle of the procedure.
• Note down your mobile network’s APN settings, which are required to make mobile data work. Go into Settings » More » Mobile Networks, click on the APN that is in use, then note down the setting for each field. While APN settings should be automatically restored from the network, you can enter them manually if needed to make mobile data work. You may also find your APN details here.
• Backup all personal data on your phone to make sure you have a copy of your personal data (e.g., contacts, SMS, MMS, Internet settings, Wi-Fi passwords, and the like) in case the procedure in this guide erases such data.
  • For backup tips, check our guides on how to sync your data to the cloud and how to create local backups of your mobile data.

Instructions

1. Copy the CyanogenMod 9.1 package and the GApps package into your phone's internal SD card.
2. Extract fastboot-win32.zip into the C:\ drive (root directory) of your computer.
3. Copy recovery-nozomi.img into the same folder where fastboot.exe has been extracted.
4. Open the CyanogenMod 9.1 ZIP file and extract the boot.img file into the same location as fastboot.exe.
5. Turn off your phone.
6. Reboot the phone into Fastboot Mode by holding down the Volume Up key as you connect the phone to your PC via USB cable.
7. On your computer, open a command prompt window as Administrator (i.e., click Start > All Programs > Accessories and right-click on Command Prompt, then select Run as Administrator from the context menu).
8. At the command prompt, enter the following command to change into the directory where the Fastboot files were extracted to:
   • cd c:\Fastboot
9. Check whether Fastboot is able to communicate with your phone by entering the command below.  If you see your phone's serial number, proceed to the next step.  Otherwise, check whether your phone's drivers are properly installed on your PC.
   • fastboot devices
10. Flash ClockworkMod Recovery to your phone by entering the following command:
    • fastboot flash boot recovery-nozomi.img
11. If successful, you see a “finished/OKAY” message on the command prompt.  If not, try this command:
    • fastboot -i 0x0fce flash boot recovery-nozomi.img
12. Reboot your phone into Recovery Mode by entering the following at the command prompt:
    • fastboot reboot
13. Your phone ought to boot into Recovery Mode.  While in Recovery Mode, use the Volume keys for scrolling and the Camera button for selecting.
14. On the recovery menu, select Install ZIP from SD card > Choose ZIP from SD card and select the CyanogenMod 9.1 package file.  Confirm that you want to install the package.
15. Install the GApps package in the same manner as in step 13.
16. Return to the main recovery menu.
17. Select Wipe data/factory reset and confirm the action on the next screen.
18. Select Wipe cache partition and confirm the action on the next screen.
19. Select Advanced > Wipe Dalvik cache and confirm the action on the next screen.
20. Power off your phone.
21. Reboot the phone back to Fastboot Mode as in step 6.
22. On the command prompt on your computer, enter this command to flash the kernel to your phone:
    • fastboot flash boot boot.img
23. You will see “finished/OKAY” on the command prompt once the kernel is successfully flashed.
24. Reboot your phone into Normal Mode by enter the command fastboot reboot at the command prompt.
25. The first time your phone boots into the new ROM, startup can take around 5 to 7 minutes.

Excellent! You have now finished installing Android 4.0.4 Ice Cream Sandwich via CyanogenMod 9.1 custom ROM on your Sony Xperia S LT26i. Try it out for yourself and play around with the different features and customization options!