Chosen Solution
My imac was running a lil slow and would crash here and there and after updating to yosemite, when I would start my mac would get a black screen….i can get it up after unplugging and doing that a few times. error message received after running hardware scan is 4MOT 4 40000003:HDD-1321
Your HD fan is failing. It needs to be replaced. If this answer is acceptable please remember to return and mark it.
