I’ve been having this issue with my 2008 Scion xB, which is the no start, no crank with a humming/buzzing sound. I bench test the starter vs the new starter and the new starter was stronger, so I replaced the starter and I still had the same problem. So, I did a little more research about testing the wires and found out that I have a bad ground somewhere. So, my quick fix was to ground the starter directly to the battery and it started right up. I will order some ground wires and replaced them all in the near future, but for now I’m happy it’s running again. I hope this helps those with the same issues.

 

The bad ground is almost always the main engine ground directly under then air box. You'll need to remove the air box and battery to get to it.