How to Diagnose the Failure of MacBook Pro HDD Cable?

MacBook Pros are innovative and secure machines getting their share of major improvements and updates with a new release every year. The level and quality of their performance have improved significantly, but they still are not perfect and may face certain issues, just like any other devices do.

Professionals report that one of the most common issues in the work of MacBook Pros is the failing hard drive. This conclusion is based on the frequency of the users applying to the Apple service or non-official services with the request to replace the hard drive which has failed.

Failure of the hard drive cable – a new common problem

A new problem with the MacBook Pros has been on the rise lately: their hard drive cable happens to fail. An HDD cable of a MacBook Pro looks like a tiny flat ribbon which connects a device’s hard drive to its logic board; besides, it is also connected to the sleep light.

Based on the number of hard drive cable failure cases reported, the problem has taken a considerably large scale. The fact that it’s hard to diagnose makes things more complicated. Cable failure would act exactly the same as an OS with its hard drive failing, only that the drive passing a flying colors SMART test. Such disparity confuses the experts who are trying to detect and fix the problem. While regular desktop SATA cables would go bad next to never, the HDD cables in MacBook Pros happen to be in need of replacement rather often recently.

What a cable’s failure causes to a MacBook Pro is no freeze or crash. A device would just randomly ‘hang’ for a short time, and then be back to normal. It looks exactly like what would happen to hard drive with a big number of blocks on it. Detecting the real problem may take quite much time. This is why users and experts have been trying to find an easy and precise way to spot the failure.

Physical wear of the HDD cables

A hard drive cable of a MacBook Pro looks like a flat ribbon formed out of five thin copper tacks, covered with a thin coat of insulation, and attached to the SATA connector at its seven pin side. Such cables may crack in traces due to impact, aging, vibration, heat, etc. Some experienced users tried carrying out a continuity test on these tracks with the help of a multimeter. What they found out was that in all the failed cables, one of the five tracks was broken at the very same place. At the point where a cable is supposed to pass over the optic drive, it did a tight bend to the right angle. At this spot, a cable would flex, and break one of its copper tracks. In an attempt to flex the cable, the track would break the contact.

What has Apple done? The problem became known to Apple, and in all versions of MacBook later than 2012, they have modified the mount of HDD, so that the case would no longer press on the hard drive cable. Besides, they have replaced the original cable 821-1480-A with an upgraded one 821-20-49-A. Unfortunately, the new cable would still eventually break.

How can you fix the cable failure?

  • Some users in DIY YouTube videos would insulate a hard drive cable with a small piece of tape to protect the tiny scraped area, or they’d tape the cable directly to the optic drive, not to let it flex. Of course, you can’t be sure that this would fix or prevent the problem, but you still can try it.
  • A good way to check if the problem with a MacBook Pro is caused by the failure of its hard drive or due to the HDD cable being broken is to connect its HDD or SSD externally, using a dock or a cable SATA to USB. The external enclosure will bypass the internal SATA cable. Next, you should watch if your MacBook boots up correctly. To select the external drive, you need to hold the Alt key down while starting your MacBook.
  • Attach the latest version of the cable 821-1226-A for macOS High Sierra. Reportedly, this cable works with no issues.
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