Originally Posted by thsheng
fastboot flash kernel diag_kernel_5.0.0
That command would incorrectly flash the diags kernel image onto the main kernel.
If you type "fastboot" with no parameters, it displays usage information, including the flash partition names:
kernel = primary kernel
diags_kernel = diags kernel
Now you need flash to the main (primary) kernel with a main kernel image, and the diags kernel with a diags kernel image.
Depending on what filenames you are using, your fastboot commands should look something like this:
fastboot flash kernel main_kernel_5.0.0.img
fastboot flash diags_kernel diag_kernel_5.0.0.img
You can also flash the diags partition with fastboot, but the main partition is too large, so you need to flash it with the "dd" command in a diags SSH command shell.
When using a guide, it is important that you follow the instructions in that guide. Those instructions were provided for a good reason, and setting off in your own direction contrary to those instructions can cause additional problems for you. I suggest that you follow the instructions in the guide more closely next time.