Getting Rid of Gremlins in your Mac - SMC and PRAM

Have you ever noticed strange behavior in you Apple Mac computer? It may be the system not sleeping when you close the lid, bluetooth devices not pairing , bluetooth turning itself off , or even bootcamp ignoring your default drive settings. 

Enter the System Management Controller (SMC). It takes care of a number of low level functions on you Mac / Macbook. 

From Apple's web site: 

The SMC is responsible for these and other low-level functions on Intel-based Mac computers:

  • Responding to presses of the power button
  • Responding to the display lid opening and closing on Mac notebooks
  • Battery management
  • Thermal management
  • Sudden Motion Sensor (SMS)
  • Ambient light sensing
  • Keyboard backlighting
  • Status indicator light (SIL) management
  • Battery status indicator lights
  • Selecting an external (instead of internal) video source for some iMac displays

Strange Bluetooth Behavior 

Yesterday, I ran into an issue where I could not pair my Apple trackpad or magic mouse to my Macbook Pro. It would recognize the device when plugged into USB port, but it would not connect via bluetooth. Existing devices would not connect, and new devices would not appear in the "add devices" bluetooth preferences screen. 

First, I rebooted my Macbook Pro. The result was that bluetooth was off and could not be turned on. I would click the "turn on" button. The bluetooth status would change to "on" for about .2 seconds and return to off.

Finally, I looked up the SMC reset procedure on Apple's website, which is to

  1. Choose Apple menu > Shut Down.
  2. After your Mac shuts down, press Shift-Control-Option on the left side of the built-in keyboard, then press the power button at the same time.
  3. Hold these keys and the power button for 10 seconds. If you have a MacBook Pro with Touch ID, the Touch ID button is also the power button.
  4. Release all keys.
  5. Press the power button again to turn on your Mac.  

When my Macbook booted up, bluetooth was turned on. I removed all paired bluetooth devices and paired them successfully. Both my trackpad and magic mouse worked wirelessly again, resolving the issue. 


How to Reset the SMC