Mac shuts down randomly

Upon further, further research, (and I have the same problem with my notebook) I found this, and I'll just quote:

"I bet you leave your system plugged in most of the time.

What is happening here is SMC thinks the power level is below the set threshold so it needs to power down the system into deep sleep mode. So how to fix? It's quite simple you need to do a SMC reset and cycle the battery a few times by fully discharging it and recharging it. That way the setpoint is memorized correctly."

I had previously done some fake SMC resets, according to bad instructions.

Please note that my first instructions above on resetting the SMC are BAD INSTRUCTIONS. And they're not what Apple says to do. Apple says to unplug the MacBook before, then hold those buttons for 10 seconds, my first reply above says to plug it in, and doesn't say anything about holding the buttons!!!!! Sorry about that!!!!

So I did a proper SMC reset, after I charged my battery to 100% with the original charger, and followed Apple's instructions exactly, on the link above. Please note that your late 2013 MacBook Pro does NOT have a removable battery. So far my MBP (mid 2014 retina 15") hasn't gone into deep sleep spontaneously. Now I just have to discharge the battery fully a few times.

Also I want to recommend Hardware Monitor (or Hardware Monitor Lite) instead of Temperature Gauge Pro. Hardware Monitor is free, and will work on all but the very newest MacBooks. You can't get it on the App Store, but it is a reputable company.

After reading lots of forums to fix problems on my Macs, I'm very wary of any knee-jerk "let's replace the motherboard" response from a Genius who can't figure out what is wrong. Easy for them, expensive for you. Do a little more research before you let them be slackers.

Upon further research, an expert has recommended:

Use an original Apple power supply of the correct wattage for your computer. Reset the SMC properly:

Reset the System Management Controller (SMC) on your Mac - Apple Support

if that doesn't work,

try some better diagnostic software, like coconutBattery and also Temperature Gauge Pro from TunaBelly.

See if you notice anything abnormal.

To fix your problem without replacing the motherboard, you may need to take the heat sink off from the CPU and (if you have one) GPU and reapply the thermal paste, and while you have it open, clean all the dust out from everywhere.

Did you reset the SMC properly? There are a few different ways to do it, according to the interwebz. This method looks like it applies to your computer, since a late 2013 retina 15" MacBook Pro does _not_ have a battery that you are supposed to be able to remove (ha laugh ha, so ridiculous, and actually, yes you CAN replace it without Apple's help)

If you don’t have a removable battery:

• Shut down your MacBook Pro
• Plug in the original power adapter
• Press (not hold) Shift-Control-Option (alt) and the power button at the same time and release all at the same time
• Press the power button to turn on your MacBook Pro

I had the same problem with my MBP. After trying all of the solutions I could find here, I finally broke down and had Apple look at it. They told me that it was the motherboard that was bad. After they replaced the motor board under warranty, it has run flawlessly ever since.

What is the "motor board" connected to? A computer or a boat? Watch that spelling Allan. This one was a doozy. You can't turn "motor" into "mother" without messing up two letters. 😁 Then to make matters worse you turned "motherboard" into "motor board." 🙂

The spellchecker changed it for me.

I'd cut that things throat. Mine makes changes too that I have to watch. PITA!