The preferred way to bring up the FieldTest application on the iPhone is to type *3001#12345# and press Call. My iPhone always responds with the error "Error performing request. Unknown Error." Here is a way to always have the FieldTest icon always appear on the Springboard.
- Bring up a terminal on the iPhone, or ssh into the iPhone.
- Become root by typing su [enter]. The default password for root is "alpine"
- Change to the FieldTest.app folder by typing: cd /Applications/FieldTest.app [enter]
- Make a backup copy of Info.plist by typing: cp Info.plist Info.plist-factory
- Change the Info.plist file to xml format by typing: plutil -c xml1 Info.plist [enter]
- Edit Info.plist using vim or nano and delete the following lines:
<key>SBAppTags</key>
<array>
<string>hidden</string>
</array> - Change the Info.plist file back to binary format by typing: plutil -c binary1 Info.plist
- Restart Springboard by typing: killall -15 SpringBoard
If you find yourself in a bind and want the old Info.plist back, you can restore the factory copy.
- Bring up a terminal or ssh into the iPhone.
- Become root by typing su [enter]
- Change to the FieldTest.app folder by typing: cd /Applications/FieldTest.app [enter]
- Restore the factory Info.plist file by typing: cp -f Info.plist-factory Info.plist [enter]
- Restart SpringBoard by typing: killall -15 SpringBoard [enter]