I have included the files needed to mass erase the flash of the MCU and re-program another binary.
The procedure is shown in the folder " FRDM-KW31_FAT_added_2019"
1) update the debugger with bootloader mode (press reset and plug in usb cable) drag and drop .sda file on MSD bootloader.
2) unplug and re-plug USB. program the flashloader_loader_mkv31f512.bin by dragging and dropping the binary on to the virtual mass storage device FRDM-KV31 which appear when you plug the USB cable from the FRDM-KV31 to the PC.
3) Open a CMD prompt window and navigate to the folder the files were unzipped to.
4) Determine the COM port by using the device manager
5) from the CMD prompt run the batch file