A mechanic told me how to enter the service menus on the cab display. Hold the alarm silence button while pushing 1,2,3. I forgot the sequence to clear codes after a repair.
Hold the number 4 down and then push the 1,2,3 in order to get into the diagnostics. You can see two modes, mechanical and electrical. You can't erase any of the mechanical codes. You can get access to erasing the electrical codes by holding the number 4 down again while pressing the 1,2,3 in order again. If I remember right it will let you erase one code or all of them. It's been awhile so you might have to read and interpret what you see on the screen to get the final clear. Here is a video showing how a Dash 8 works. I believe it is the same as a Dash 10.