Originally Posted by geekmaster
Like knc1 said, the dd command that you used trashes your mmc contents. Luckily, the K4 and K5 protect some of that storage space that contains critical identifying information (serial number, etc.) that are NOT backed up in mmcblk0.img (write-only areas), but on a K3 you could have caused difficult problems.
You should install a kernel image with fastboot, not dd. /dev/mmcblk0 is the entire mmc, not the location of a kernel.
Start the debricking process over, and this time follow the instructions (flash kernels only with fastboot).
How can I install both Kernels (diags, main)? this because in fastboot when i use this command: fastboot flash kernel DIAGS KERNEL 5.0.0.img and after fastboot flash kernel main Kernel 5.1.2.img, the second one delete the first one and the device dont start in diags screen.