Decoding OS X’s startup error signals – What do they mean?

Ever have your iMac display a gray screen with a flashing question mark? How about the universal no sign? What about the time it started beeping and wouldn’t start up. Macs aren’t perfect. Sometimes things go wrong and they break. Whether its something you did or not, things happen. To figure out what is wrong, you have to decode these error messages. Here’s what they mean and what to do about them:

Macintosh Startup Errors in OS X:

1. Screen is black, no power, nothing:

The unit isn’t receiving power to turn itself on. Check the battery and charger. Hold down the power button for 5 seconds until you are sure the computer is off, then try to restart it. If it still refuses to power on, then it’s a hardware problem requiring service. Either the logic board or the DC board is damaged. If it powers up with a charged battery but not A/C, its the DC board.

2. Screen is black, the power light goes on but computer does nothing:

This means either the Power On Self Test (POST) has failed or the Boot ROM has failed. You have a hardware problem. The computer is receiving power but doesn’t want to turn on. Most likely cause is logic board damage. In my experience, this is common with liquid damage / spills shorting out the motherboard.

3. Screen is black with a flashing power light once per second:

Check your RAM and make sure it’s seated properly. This means that either the computer isn’t seeing its RAM or that the RAM is bad.

4. Screen is black with the power light continuously flashing 3 times with a pause in between:

Check your RAM. This means that the Mac is seeing it’s RAM but doesn’t like what it sees. Reseat the RAM and try again.

5. Gray screen with a circle and slash (the International “no” sign):

This means your Mac could not load it’s boot routines (EFI). Try booting from an external drive or the OS X DVD. If that works, then you need to reinstall OS X. If you can’t reinstall, the hard drive may be bad. A PRAM reset may also fix this by resetting the Startup Disk.

6. Gray screen with flashing folder and question mark:

This means your Mac can’t see the hard drive or an OS X volume. Either the drive’s connection is bad, there is no installation of OS X or the drive itself is shot. Try booting from an external drive and see if you can see the drive.

7. Gray screen with a flashing globe:

Your Mac is set to boot from a NetBoot Server and is looking for it. Check the network connections if it doesn’t find the server after a reasonable amount of time.

While these error symbols are primarily seen with Intel Macs, on the Power PC side, they also translate. The difference between the two of the is the icon size and picture of the symbol. Power PC Macs will also let out beeps instead of flashing the power light to signal RAM issues. Lastly, Power PC’s don’t have EFI in their boot routine. They use Open Firmware.

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