Hardware test error: 4SNS/1/40000000: TN1D-128.000

You have a sensor problem.

Specifically

N: North bridge (motherboard controller)

http://www.macissues.com/2014/03/21/how-to-run-and-interpret-apples-hardware-tes ts-on-your-mac/

Is the Northbridge sensor woring or running hot?

Install a temp monitoring ap and find out. I use Macs Fan Control.

Also see:

Why is my Northbridge Chip running at dangerously high temperatures?

http://forums.macrumors.com/showthread.php?t=1169024

http://www.xlr8yourmac.com/archives/jul14/071114.html

If you have a wiggly Northbridge chip as others have experienced, read the thread referenced below (applies to 2009 through 2012 models). The Original Poster thought he just had random crashing, but as he probed, the NorthBridge heatsink and its retaining pins became the focus. Richard Schlettyprovided some good photographs (toward the end) as well.

Re: Kernel panic in Yosemite 10.10.3