Disable the Sudden Motion Sensor on a Mac Laptop

The Sudden Motion Sensor is designed to protect your Mac hard drive in the event of a computer being dropped or an unusually strong vibration. Essentially what it does is park the hard drive head when movement is detected, which prevents it from potentially scooting across the disk surface and scratching or otherwise damaging the drive or drive head.

Generally speaking, you will want to always have the SMS sensor enabled, but if you’re like me and have replaced the stock hard drive with a Solid State Hardrive. then this setting is not-required. Further more, like me, if you’re using an Intel 320 SSD you definitely want to disable this setting, because if activated it could render your disk non-functioning and cause the dreaded 8mb failure.

Disable Sudden Motion Sensor on a Mac Laptop

This works to disable the Sudden Motion Sensor on the MacBook Pro, MacBook Air, MacBook, PowerBook, and iBook running Mac OS X 10.6 (Snow Leopard), 10.7 (Lion) and 10.8 (Mountain Lion)

  1. Launch Terminal
  2. Type the following at the command line: sudo pmset -a sms 0
  3. Hit return and enter your password

The SMS sensor is now disabled, it’s just as easy to reenable again by changing the zero to a one when you need the protection back:

Enable the Sudden Motion Sensor on a Mac Laptop

This works on the same hardware as disabling the feature, and it’s basically the same commands:

  1. Launch Terminal
  2. Type the following at the command line: sudo pmset -a sms 1
  3. Hit return and enter your password

The SMS sensor is now enabled, you’ll notice the commands are identical except that the -a sms flag now has 1 attached to it rather than 0 (standard computing protocol of 1 for on, 0 for off).

Checking the status of the Sudden Motion Sensor

If you’re not sure whether the motion sensor is enabled or not, you can check quickly with the command line:

  1. Launch Terminal
  2. At the command line, type: sudo pmset -g
  3. Hit return, enter your password
  4. In the list of settings look for the sms entry. Seeing a 1 next to sms indicates that the motion sensor is enabled, seeing a 0 next to sms indicates the motion sensor is disabled.

1 comment

  1. OMG I got the same drive in my 15″ MacBook pro, and the same thing happened to me 9 months ago and I thought my drive was cactus. Took me ages to find the solution that time round, this solution is great and easy to find in google. Don’t forget you need to reset this each time you upgrade the OS. Also, get Trim enabler (http://www.groths.org/?page_id=322) you’ll need that too.

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