Step 1: Open Cydia on your iPhone 4 or 3GS
Step 2: Go to Manage->Sources
Step 3: Now tap on “Editâ€, then tap on “Addâ€
Enter the following repo
http://cydia.pushfix.info
Now tap on “Add Sourceâ€
Step 4: Tap on Done.
Step 5: Tap on Pushfix.info and install
Step 6: After the installation Go to Pushfix.info again. Now scroll down and look for “Ultrasn0w fixer for 4.3.1†Tap on it. Install the package. It will ask you to reboot your device.