MacBook Will shut down during start up.

Question

Why does my Mac book shut shut down during startup?

Answer 1

What to do if your Mac won’t boot up
First, try resetting your SMC.
Resetting the SMC of an Intel-based portable Mac with a battery you should not remove on your own
Note: This will not delete any data.
The SMC is responsible for controlling various system functions. None of your data will be deleted by resetting the SMC.
Shut down the computer by going to Apple () > Shut Down…
Select Shut Down or allow the computer to shut down automatically.
Plug in the MagSafe power adapter into a power source and then connect it to your Mac if you have not already done so.
On the built-in keyboard, press the (left side) Shift (⇧), Control (⌃), and Option (⌥) keys and the Power Button at the same time.
Release the (left side) Shift (⇧), Control (⌃), and Option (⌥) keys and the Power Button at the same time.
Resetting the SMC of an Intel-based Mac Pro, iMac, Mac mini, or Xserve
Note: This will not delete any data.
The SMC is responsible for controlling various system functions. None of your data will be deleted by resetting the SMC.
Shut down the computer by going to Apple () > Shut Down…
Select Shut Down or allow the computer to shut down automatically.
Unplug the computer’s power cord.
Wait fifteen seconds.
Attach the computer’s power cord.
Wait five seconds and then press the power button to turn on the computer.
Resetting the SMC of an Intel-based portable Mac with a removable battery
Note: This will not delete any data.
The SMC is responsible for controlling various system functions. None of your data will be deleted by resetting the SMC.
Shut down the computer by going to Apple () > Shut Down…
Select Shut Down or allow the computer to shut down automatically.
Plug in the MagSafe power adapter into a power source and then connect it to your Mac if you have not already done so.
Remove the battery.
Press and hold the Power Button for 5 seconds.
Release the Power Button.
Reconnect the battery and the MagSafe power adapter.
Press the Power Button to turn on the computer.
Then, try resetting your PRAM.
Resetting the NVRAM/PRAM
Note: This will not delete any data.
The NVRAM/PRAM stores information such as speaker volume, screen resolution, startup disk selection, and recent kernel panic information (if any). You should reset the NVRAM/PRAM if you experience issues relating to these functions.
Shut down the computer by going to Apple () > Shut Down…
Select Shut Down or allow the computer to shut down automatically.
Turn on the computer by pressing the Power Button.
On the built-in keyboard, press and hold the Command (⌘), Option (⌥), P, and R keys before the gray screen appears.
Continue to hold down the keys until the computer restarts and you hear the startup chime for the second time.
Release the keys on the built-in keyboard.
Then, try repairing the disk using Disk Utility.
Repairing a disk using Disk Utility on the Recovery HD.
Note: This should not delete any information or files from the disk.
Repairing a disk can help solve various file-related issues.
Make sure the computer is powered off before continuing.
Press the Power Button to turn on the computer.
Press and hold both the R and Command (⌘) keys on the keyboard until the Recovery partition loads. If this does not work, shut down the computer, press the Power Button to turn on the computer, and then hold in the Alt (⌥) button immediately after you press the power button. Then, select the Recovery HD partition to boot up in the Recovery HD partition.
Select Disk Utility.
Once you are in the Disk Utility app, select the drive from the sidebar on the left.
Then, choose the Repair Disk button on the right.
If the Repair Disk button is grey or unavailable, select Verify Disk and then select Repair Disk.
If this does not solve your issues, you may have no choice but to reformat the drive using Disk Utility.
You should also repair your startup disk’s disk permissions as well.
Repairing a disk’s permissions using Disk Utility on the Recovery HD.
Note: This should not delete any information or files from the disk.
Repairing a disk's permissions can help solve various file-related issues.
Make sure the computer is powered off before continuing.
Press the Power Button to turn on the computer.
Press and hold both the R and Command (⌘) keys on the keyboard until the Recovery partition loads. If this does not work, shut down the computer, press the Power Button to turn on the computer, and then hold in the Alt (⌥) button immediately after you press the power button. Then, select the Recovery HD partition to boot up in the Recovery HD partition.
Select Disk Utility.
Once you are in the Disk Utility app, select the drive from the sidebar on the left.
Then, choose the Repair Disk Permissions button on the right.
If this does not solve your issues, continue on and run Apple Hardware Test.
Using Apple Hardware Test to troubleshoot a hardware problem
Your issues might be caused by a hardware problem. Running Apple Hardware Test can help you solve this problem by showing you the faulty hardware.
Shut down the computer by going to Apple () > Shut Down…
Select Shut Down or allow the computer to shut down automatically.
Plug in the MagSafe power adapter into a power source and then connect it to your Mac if you have not already done so.
Press the Power Button to turn on the computer.
Press and hold the D key on the keyboard before the grey starting screen appears.
Continue to hold the D key until the loading screen shows up. You should see a globe.
When AHT has loaded, select your Language and then press the Return (↩) key.
Select the Perform Extended Testing checkbox located under the Test button.
Press the T key, select the Test button, or press the Return (↩) key to start running the diagnostics.
Report any issues it shows in a reply.
If Apple Hardware Test does not show any issues, continue on and reinstall OS X.
If Apple Hardware Test does show any issues, report them in a reply.
Reinstall OS X
Note: This will not erase any data on the disk. However, it is highly recommended that you create a backup before continuing.
Reinstalling OS X can solve various problems such as corrupt system files.
Shut down the computer by going to Apple () > Shut Down…
Select Shut Down or allow the computer to shut down automatically.
Plug in the MagSafe power adapter into a power source and then connect it to your Mac if you have not already done so.
Press the Power Button to turn on the computer.
Press and hold both the R and Command (⌘) keys on the keyboard until the Recovery partition loads.
Select Reinstall OS X and then choose Continue.
Follow the instructions.
If your computer still does not boot up
If your computer still does not boot up, it may be due to a hardware problem or software conflict.
Make an appointment with an authorized Apple service center or by making an appointment at the Genius Bar by going to this link:
http://www.apple.com/retail/geniusbar/
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