If you’re having issues with your computer lagging, freezing or just plain being sluggish it may be a hardware issue. For instance when your hard drive starts to go, you may notice apps that used to just take a second to load now take half a minute, or you may see boot up times start taking multiple minutes.

For most issues like this, the most common culprit is software. However when you’ve ruled out software as being the culprit, the next place you want to check is the hardware.

A brief introduction into the reason for this article. I own a 2012 iMac and for the longest time it was extremely fast and worked flawlessly. About a month ago I started to start having issue where my Mac would just freeze or crash. Sometimes just getting to the login screen took around 2-3 minutes. Apps took forever to load, even saving documents would take a frustratingly long time.

I went about trying to figure out the problem thinking it was a software issue. However, not even after completely reformatting my computer did the issue go away. With that kind of evidence, what else could it have been. No one wants to think it’s a hardware issue, because that involves having to open up the computer and ultimately spend money to buy a replacement part. The unfortunate truth however is that hardware can and does fail.

Here’s how to scan and identify faulty hardware on your Mac.


How to Scan for Faulty Hardware

identify hardware issue macintosh

Apple Hardware Test

To scan we are going to use the Apple Diagnostics and Apple Hardware Test tools.

  • Before you start anything, unplug all your connected devices and external drives! Leave your Keyboard and Mouse connected.
  • Restart your Mac and while it just starts to boot up hold down the option and D key. I know some sites, even the Apple site says you only need to hold down the D key, however in all my tests that never worked.

The Apple Diagnostics and Hardware Test tool has a really simple interface. When you get to the screen shown in the adjacent screenshot, just click the “Test” button. This can take a little while, in my tests it took around 6 minutes. When if finished scanning, it reported that I had a hard drive failure.

hardware mac problems

Hardware Scan Results

When the scan is completed it shows a report of its findings including how long the actual scan took. As you can see from the screenshot, the Apple Hardware test has reported an error.

The best thing to do is to either write down what the error log says, or take a picture of the screen. You can plug that data into Google and figure out for yourself what’s causing the issue.

In my case it read:

Alert! Apple Hardware Test has detected an error.
4HDD/11/40000000: SATA(0,0)

Just by looking at that I could tell that it was a hard drive failure. This was mainly because the error included “HDD” and “SATA” both which I knew referenced to the hard drive. Ultimately though just enter it into Google if you aren’t sure what the failure is referring to.

So we now know that there is a hardware issue and we know that it’s because of a faulty hard drive. Now you have to ask yourself, do you have the skills/confidence to open up, take out the old HDD and replace it with a new HDD? If the answer is no, take it to the Apple Store, this is what they are there for!

I was able to do the replacement myself, for those interested how I did it:

  1. Watched a quick video on YouTube on how to safely open up an iMac.
  2. Already knew what a hard drive looked like so it was easy to identify and remove.
  3. Bought a Kingston SSD hard drive, plugged her in.
  4. Put humpty dumpty back together, crossed my fingers and I pressed the power button.

The Mac is up and running faster than it ever has before (mainly because of the super fast SSD).

P.S. If you have to replace your hard drive, get yourself a SSD drive if possible. It’s way faster than a regular HDD.

P.S.S I know lots of sites recommend buying suction cups and all these other tools to open your Mac. It’s not really necessary if you have an iMac with a magnetic screen or a Macbook. Personally I used my (short) nails to pull off the screen since it’s magnetic, and my regular everyday toolkit and screwdrivers that I’ve owned for years to replace the faulty hardware.