So your Mac is acting wonky and you have tried rebooting. And you’ve even tried reseting the PRAM (Note: Before resetting PRAM or the SMC, back up your whole system on an external drive with Time Machine Backup App. To do this, first turn off your Mac. Next turn on your Mac and hold down the Command+Option+P+R keys, at the same time.)
You’ve seemingly done it all, but your Mac is still acting wonky! Now what? In some cases, resetting the System Management Controller (SMC) can be a resolution. This is sometimes the last simple option to restore basic level system functions to your Mac, particularly for power and hardware related issues.
Process of elimination it is a form of diagnostics. If a PRAM or SMC reset doesn’t fix your issues, you might want to see a ACMT (Apple Certified Macintosh Technician) because your Mac could have a hardware failure.
So what does the SMC do? The SMC controls most power functions on newer-model Macs. Resetting the SMC can resolve some computer issues such as no start up, no display video, sleep issues, fan issues, battery and so on. Resetting the SMC is not a cure-all, but it’s a good last-resort before bringing your machine in for service.