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How to Keep a Mac Efficient and Well Maintained: Part 3

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Macs, like all computers, are prone to break down eventually. With continuous use, the efficiency can decrease and a Mac may start behaving erratically due to a physical component failing. This could be a logic board, RAM, or internal fan. Files may not open, search may become slower or irrelevant, apps may start misbehaving and more.

You can minimise both the number and the severity of problems with a maintenance regimen. 

In the third part of the tutorial, I’ll show you how to:

  • Take advantage of Apple Diagnostics to reveal hardware problems
  • Monitor and maintain the health of the hard drive

Use Apple Diagnostics to Determine Hardware Problems

The hardware components of a Mac are fairly robust. Over time faults may start to develop and although the Mac may continue to function, some faults lead to hardware or software instability.

Apple Diagnostics or older Apple Hardware Test is a comprehensive tool to determine problems with a Mac’s internal hardware. This includes the logic board, memory, battery or power adapter, sensors, graphics and wireless components. The tests ensure that all the components and sensors are working.

There are number of ways to run Apple Diagnostics or Apple Hardware Test. Although their appearance and name are different, they both test the hardware for problems. It depends on the model and year it launched.

  • Since June 2013: Macs use a new hardware testing system called Apple Diagnostics. It comes on a hidden disk image, or can also run over the internet
  • Mid 2011 to June 2013: Apple discontinued the optical drive. These Macs run the Apple Hardware Test from Recovery HD volume. If that’s not available they run from the internet
  • Up to mid 2011: Macs with optical drive came with an OS X install disc 

Apple Diagnostics Test Procedure

Step 1

If you’ve a DVD or USB drive with Apple Hardware Test tools on it, then insert it into the Mac. If the Mac does not include an external boot media, ensure the Mac is connected to the internet.

Step 2

Disconnect all external devices except keyboard, mouse, display, ethernet cord, and AC power. If you’re testing it on a laptop, ensure to connect to AC power. Also ensure that mouse and keyboard runs through wired USB instead of bluetooth.

Step 3

Ensure that the Mac is on a hard, flat, stable surface with good ventilation.

Step 4

Choose Apple Menu > Shut Down and wait for the Mac to shut down completely.

Step 5

Turn on the Mac, then immediately press and hold the D key on the keyboard. Continue to hold down the key until the Mac’s grey screen changes to either Hardware Test or Apple Diagnostics.

Step 6

Hold Option-D to force the system to load the tools from the Internet.

Continue to hold down the keys until you see a Starting Internet Recovery message on the Mac. Choose the network from the drop down menu and wait until the language screen appears.

Skip this step if the Hardware Test or Apple Diagnostics starts successfully either from the USB drive or Recovery HD volume.

Step 7

Select a language and click the right arrow button or press Return key.

Step 8 for Apple Hardware Test

Click the Hardware Test tab. Apple Hardware Tests supports two types of test—a standard and an extended test. 

Click the tick in the Perform Extended Testing box and click the Test button. The latter test takes more time to complete but is thorough.

If the test goes smoothly, the test area either displays No trouble found or puts the word Passed next to all the applicable tests.

Step 8 for Apple Diagnostics

The test runs automatically, and takes few minutes.

If the test goes smoothly, it either says No issues found or lists the problem along with the details.

Step 9

During the course of the tests, you may hear the fan spin up and down, but this is a part of the process. In modern Macs, you’ll see a grey progress bar saying Checking your Mac… with approximate time remaining. 

At the end, click Restart to restart the Mac.

Checking the Mac indicator during Apple Diagnostics Checking the Mac indicator during Apple Diagnostics Checking the Mac indicator during Apple Diagnostics
Checking the Mac indicator during Apple Diagnostics 

What to Do if Apple Hardware Tests Won’t Start

Apple recommends that you should shut down the computer and press and hold the key D until the grey screen appears. If the grey screen fails to appear, wait for the Mac to startup, then shut it down and repeat the process.

If you’re reinstalling an older computer from scratch and lost the original disks that came with Hardware Test tools, then diagnostic tools might no longer be available. It is possible to restore the Hardware Test tools. Use the following terminal commands to determine the model and board ID of the Mac.

sysctl hw.model | awk '{ print $2 }' ioreg -l | awk -F\" '/board-id/ { print $4 }'

Go to Apple Hardware Test Github Page and download the relevant package for your Mac. Copy the package to

/System/Library/CoreServices/.diagnostics folder, then reboot while holding D to start the diagnostic tools.

Interpret the Results

When the test encounters any errors, a failure message will appear along with reference code and a brief description. For instance

  • NDK001, 003, 004—issue with the keyboard
  • NDC001, 003…to 006—issue with the camera
  • NDR001, 003, 004—issue with the trackpad
  • PFM001, 002…to 007—issue with the SMC
  • NDL001—issue with the bluetooth hardware
Diagnostics result of a MacDiagnostics result of a MacDiagnostics result of a Mac
Diagnostics result of a Mac

If you encounter any hardware errors, you have to take the Mac to the nearest Apple Store and get the parts replaced. Ensure that you note the error code and warranty before you call Apple Support. 

You should run Apple Diagnostics Tests:

  • Whenever you install new RAM or any new hardware component
  • When you begin to have problems that Disk Utility or OS re-installation do not solve
  • When you have a Mac older than three years

Alternatives to Apple Diagnostics tools

There are many third party utilities out there which can perform specific types of hardware testing and provides you more information.

  • Memtest—finds intermittent memory problems that are the frequent cause of unexplained crashes or freezes in Macs. Users running Mac OS X 10.6.8 or earlier must download version 4.22. For 64-bit Macs download version 4.23
  • Techtool Pro—a comprehensive application to check for filesystem errors, I/O errors, Power On Self-Test (POST) errors, Internal battery condition, hard drive health (SMART), bluetooth hardware and network adapters. The app costs $99 but gives you a detailed information much beyond the Apple Diagnostics
  • Atomic—a dedicated RAM checker that can detect problems with your memory by using a variety of memory testing techniques. The app costs $29.99 and can detect problems beforehand

Monitor and Maintain the Health of a Hard Drive

Over time, almost all disks can develop minor errors. Since these errors can occur during normal computer usage, it is essential to monitor and maintain the discs periodically. Frequent errors can damage the filesystem, which in turn can lead to slowdown, crash, or worst data loss.

Reparing a hard drive is typically more of a troubleshooting step than a maintenance step; but given the frequency of random disk errors, hard drive failure rate, and occasional erratic symptoms, it is justifiable considered a preventive measure.

Monitor the Health of a Hard Drive

Most modern hard drives and SSD have built-in sensors and monitoring circuitry that form a system called SMART which means Self Monitoring, Analysis, and Reporting Technology.

The purpose of this technology is to give reports on various indicators of the drive reliability with the intent of detecting imminent hardware failure before it happens.

To check your drive’s SMART status, open Disk Utility, found in in Applications > Utilities, and select the drive in the list on the left. If the selected drive supports SMART you'll see this message at the bottom of the window: S.M.A.R.T. Status: Verified.

SMART status verification in disk utility appSMART status verification in disk utility appSMART status verification in disk utility app
SMART status verification in disk utility app

If you see About to Fail in red letters, backup the drive immediately although it’s hard to say how much data you’ll be able to backup. Even if Disk Utility solves the problem, you should backup the data and replace the disk as soon as possible.

If the Mac has a fusion drive, or if you’ve enable FileVault then Disk Utility may not show SMART status, even if your hardware supports SMART. Open System Information, select Storage in the list on the left, and look for SMART  status on the right.

SMART status from System InformationSMART status from System InformationSMART status from System Information
SMART status from System Information

Although Disk Utility reports SMART status you’re not getting a constant, real-time, report of drive reliability and their parameters. There are many third party utilities which monitor SMART status in detail and alert you of any change.

Smartmontools is a command line utility consisting of two packages—smartctl and smartd. They control and monitor storage system using SMART and give you information about ongoing disk degradation through various stats. 

Backblaze uses these reliability stats to predict hard drive failure.

  • SMART 5—Reallocated sectors count
  • SMART 173—Wear levelling count
  • SMART 187—Reported uncorrectable errors
  • SMART 197—Current pending sector count
  • SMART 198—Uncorrectable sector count

Download and install the latest package. Open Terminal and type in diskutil list. This command will populate all the disks, whether internal or external, with their size and identifier id.

List of hard disks by using diskutil command List of hard disks by using diskutil command List of hard disks by using diskutil command
List of hard disks by using diskutil command 

Type in

smartctl -a /dev/identifier id Replace identifier id with the drive id.

This command generates a long report of that drive. If the RAW value for any of these stats is greater than zero, than there is a need to investigate, although you may also see the value column in percentage. Anything less than 60% is a cause of concern.

smartctl command result for my SSDsmartctl command result for my SSDsmartctl command result for my SSD
smartctl command result for my SSD

You can also try out these third party utilities which gives you more features and a nice user interface.

  • SMARTReporter—is a utility based on SMART It also checks for I/O errors or RAID (Redundant Array of Inexpensive Discs) degradation. It is available on the Mac App Store at $5.99
  • SMARTUtility—This utility is again based on SMART. SMART Utility not only displays the individual attributes to see their status and information, but it also uses an internal algorithm based on those attributes to detect drives failing before SMART indicates it has failed. It is available for $25
  • DriveDX—It offers a complete, extensive drive checking and monitoring tool available for Mac at $20. It comes with a intuitive, interpretive UI, which helps you what each attribute means. It also performs overall drive health diagnostics using drive health indicators that most closely correlate with drive failures

Maintain the health of hard drive

Apart from regular monitoring, you also need to maintain your hard drive. There are many use cases wherein you want to use Disk Utility.

  • After a power outage, hard restarts, and system crash—especially if a Mac behaves erratically thereafter
  • Periodically, as a part of a regular maintenance routine, to identify any hidden directory corruption before it becomes a problem
  • Software related bugs can cause bad data to be written on your disk which can corrupt data or worst data loss
  • If you eject an hard drive without unmounting the volume, you may corrupt the data as well as hard drive

Open the Disk Utility app. 

From the sidebar, select the startup volume and click the First Aid button on the toolbar. When you click RunDisk Utility will verify the disc and attempt to repair it if necessary.

Run first aid on the disk utilityRun first aid on the disk utilityRun first aid on the disk utility
Run first aid on the disk utility

If Disk Utility discovers any issue that requires a repair, you will need to start the Mac from Recovery or Internet Recovery. Wait for Utilities window to load and click Disk Utility.

Select the startup disk and click First Aid.

Disk utilities window in macOS recoveryDisk utilities window in macOS recoveryDisk utilities window in macOS recovery
Disk utilities window in macOS recovery

In the rare event that Disk Utility encounters a serious problem that it cannot solve, you may need to use third-party utilities:

  • DiskWarrior—a utility to prevent and resolve directory damage which is the leading cause of Mac instability. DiskWarrior resolves disk damage by rebuilding the disk directory using data recovered from the original directory, thereby recovering files and folders you thought were lost. At $120, this utility is a must have for repairing disc problems.
  • Techtool Pro—a comprehensive application to check for filesystem errors, I/O errors, Power On Self-Test (POST) errors, Internal battery condition, hard drive health (SMART), bluetooth hardware and network adapters. The app costs $99 but gives you a detailed information much beyond the Apple Diagnostics.


In this part of the tutorial, I’ve shown you how to keep a Mac maintained by performing a periodic Apple Diagnostics check and hard disc verification. 

The hard disc drive, or solid state drive, is an important component of a Mac and for the OS as well. While it is granted that every hard disk will eventually die after few years, you can keep yourself informed and safeguard your data with regular backups and disc maintenance.

In the next and final part of this tutorial series, I'll show you more ways to keep a Mac maintained and efficient. 

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