Is your kindle bricked, or just stuck in diags (perhaps with a dead battery)? In diags, it does not got to low power screen saver mode and can completely drain the battery. There is a menu item to disable diags in the exit menu. You may need to run the first diag in the main menu first to create a missing folder and file before "disable diags" will work.
You should be able to boot to any mode with MfgTool from the "select boot" thread, from USB Downloader (Recovery) mode. This stuff is documented in the simple debricking thread as well.