MacBook Pro sleeps unexpectedly and runs fans at high speed, even after SMC reset

Solution 1:

Run diagnostics on the Mac as follows:

1. Disconnect all external devices
2. Go to Apple Menu —> Restart
3. Immediately press and hold down the D key while your Mac restarts
4. Keep holding the D key until you see the screen listing different languages appears
5. Click English. Apple Diagnostics starts automatically.

Common results could be:

• Wi-Fi — a failure of the AirPort wireless card (4AIR)
• Hard disk and SSD (4HDD)
• Logic board (4IRP)
• Memory — RAM (4MEM)
• External disk (4MHD)
• Fans (4MOT)
• Processor (4PRC)
• Video/graphics card (4YDC)

I'd recommend you see if you have a fan issue: 4MOT