How to Perform an Apple Hardware Test - 2015

Here is great way to perform a Apple Hardware test on your Mac
over the internet.

Link for Error Codes
https://support.apple.com/en-us/HT203747

Using the Apple Hardware Test Over the Internet

The error codes
Using the Apple Hardware Test Over the Internet

If the test determines there is an error with your Mac computer, It will display an error code similar to this:

4SNS/1/1/4000000 TL0P-130

Here are what some of those errors mean

4ETH: Ethernet controller
4IRP: Main Logic board
4MLB: Logic board controller
4PRC: Processor
4HDD: Hard disk
4MHD: External disk
4YDC: Video card
4SNS: System sensor
4MOT: Fan motor
4MEM: Memory module
4AIR: AirPort wireless card
A: Ambient air sensor
B: Battery
C: Central processors (CPU)
D: DC (direct current)
e: PCI-express slot
F: FireWire port
G: Graphics processor (GPU)
H: Hard disk
h: Heat pipe (heat sink)
L: LCD display
M: Memory or memory riser boards
m: Misc. (i.e., battery chargers)
N: North bridge (motherboard controller)
O: Optical drives
P: Power bus
p: Power supply
s: Palm rests for laptops
W: Airport Wi-Fi card

Some fixes can be
resetting the system PRAM
resetting the system management controller