The MacBook family was first introduced in May 2006 and replaced the iBook as Apple's consumer laptop.

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MacBook stuck on apple logo boot screen

I have an 2008 Aluminum Macbook and when I try boot, it gets stuck on the apple logo page with the spinning wheel below it. I have tried to boot in safe mode but i get the error messsage "disc02: I/O error" . I tried next to reset the PRAM but no results. I don't have the original installation disk so I cannot boot from there. I have read that the problem may be the hard drive. Is there any way to fix this problem or is there another way to run a hd diagnostic without the startup disk if that is the problem.

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DiskXX: I/O error messages that show when booting in verbose mode do correspond to failed hard drives the majority of the time. It IS possible that either the hard drive cable or logic board is faulty but given the age of the hard drive it is much more likely to be the culprit. Either way the Disk02: I/O error messages are a clear indicator of a hardware issue that cannot be solved by software fixes.

If you have never formatted your disk or reimaged it with a new OS then you probably still have Apple Hardware Test (AHT) built in, which may help in giving you a more definitive answer. Hold down D when you boot your Mac and keep holding it down (can sometimes take 45 seconds or longer) until you see an icon that resembles a classic Mac with a chip in front of it. If this logo appears then you have AHT installed and you can run a quick test by clicking Test or an extended test by checking the box next to "Perform extended testing" and then clicking Test. Depending on the results you might see "No trouble found" which means all of the components passed testing or something more cryptic, along the lines of 4SNS/1/1/40000.... These codes tell you what component failed. If the hard drive is failing then I would expect to see a 4HDD error code.

If AHT isn't available then if I were you, based on the Disk02: I/O error, I would start by replacing the hard drive since the age and errors seen so far strongly point to that as the problem.

Hope that helps!

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I ran the extended test and the result came back as "4SNS/1/40000000: ThOH-93.750" I ran the standard test and received the code "4SNS/1/40000000: Th1H-76.625" I've tried to research the meanings of these errors and it seems to point to the heat sync system sensor. However, I don't believe this would cause my Macbook not to boot (please correct me if I'm wrong).

After restarting and running the AHT again I received the "4HDD/11/40000004:SATA(0,0)" error message. So I guess the next step is replacing the hard drive?

For the first two error messages my MacBook has been running hotter than usual. I installed smcFan Control to get a better idea of the temperatures and fan speeds about 2 months ago. Temperatures were reaching an excess of 90C. My priority is getting my computer to boot, but I would also like to resolve the heat issue as well. Please let me know if I'm in the right direction. If you know the exact meaning of these error codes, and how to resolve these issues please let me know.



It sounds like AHT just confirmed that the hard drive is physically failing so it will need to be replaced. Keep in mind that AHT is hardware specific, so once you replace the hard drive and install a fresh OS you will no longer have access to AHT without the original gray system discs. With the first two errors I think you're right in that they point to the temp sensor on the heatsink. With your particular MacBook you can replace the hard drive by just removing the battery panel. I would encourage you to also remove the bottom case (be sure to remove the battery first) and inspect the fan & heatsink for dust buildup & debris. A lot of times you'll find hair, lint, dust, etc caked onto the heatsink's fins, blocking airflow out of the machine, trapping hot air inside. You can use a small pick along with compressed air to remove any buildup or debris that you encounter. Hopefully that's all that is required to relieve the heatsink temperature issue. I would try to confirm using iStat afterwards.


Thanks for all the info. I replaced the hard drive and it booted right up. There was also a significant amount of dust buildup inside. I have removed as much as I can with a pick and will purchase some compressed air.


Great! Glad to hear it's booting again!


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