1. Check the Power
Now lets be clear, by not start up we mean the absolute worst case scenario: the display does not even flicker, the fans are dead silent, and it would seem the MacBook Pro has no power. In short, the MacBook Pro won’t start up.
Begin by isolating the MacBook Pro: unplug all peripherals except the MagSafe adapter and confirm that the laptop is receiving power by checking for the green light on on the adapter’s connector tip. If the MacBook Pro is receiving power from the adapter we can rule out a bad power outlet and a faulty adapter. If there is debris or dirt around the magnetic tip of the MagSafe adapter, take a moment to clean it using a tooth brush or cotton swab while the adapter is unplugged.
2. Think Hardware
With external parts ruled out, we can take a moment to think about user-serviceable parts. Have you recently installed new RAM or a larger hard drive? It’s possible one of these new parts has failed and is causing the problem. In order to test this, swap out the new parts for the old parts. If the MacBook Pro now starts up with the old components, then one of the new parts may be defective.
3. Reset the SMC
With what hardware we can check ruled out, our next option is to reset the SMC (Systems Management Controller). The SMC is responsible for the most low-level functions on MacBook Pros such as regulating fan speed, the battery status indicator lights, and responding to the press of the power button. Resetting the SMC will not affect your data, it will only reset the current SMC data back to the original factory settings. The procedure for resetting the SMC depends on whether you can remove the battery of your MacBook Pro or not.
For the older MacBook Pros with a removable battery: shut down the computer (if it was on I think you’ve solved the problem already). Remove the battery and unplug the MagSafe adapter. Press and hold down the power button for 5 seconds, then release the button. Reconnect the MagSafe adapter and reinstall the battery. Pressing the power button now should turn on your MacBook Pro.
If your unibody MacBook Pro won’t start up, begin with a shut down computer. Plug in the MagSafe adaptor if it was not already connected. Press and hold down the left side Shift, Control, and Option keys as well as the power button. Release all the keys and the power button simultaneously. Your MacBook Pro should now turn on if you press the power button.
4. Reset the PRAM and NVRAM
If your MacBook Pro still won’t start up there’s one final thing to try: resetting the PRAM (Parameter RAM) and NVRAM (Non-Volatile RAM). Don’t worry, the only things stored in this type of memory are very basic system settings like display refresh rates and the start up chime. Reseting these items will simply cause them to go back to their factory settings and correct any possible corruption that may have taken place. To reset the NVRAM and PRAM press the power button and immediately hold down the Command, Option, “P”, and “R” keys until you hear the computer restart.
5. Contact Apple Support
If your MacBook Pro still won’t start up it’s time to hand it over to Apple Support. When contacting Apple Support be sure to mention that you’ve already checked the power source, the adapter, ruled out a bad hard drive or RAM, reset the PRAM, NVRAM, and SMC. At the very least, it’ll save you some time on the phone and your Apple service agent will get down to business that much quicker.