Diagnosing MacBook Pro Hard Drive Cable Failure

I bought my MacBook Pro mid 2012 version back in August 2013 and I am just replaced the HDD cable for the third time.

I had kept the three old cables so I decided to find out what had gone wrong with them. There are 5 thin copper tacks, which connect to the 7 pin side of the SATA connector. I used a multimeter to do a continuity test on these tracks. I found that on all three cables one of these tracks had broken at the same place. The cable does a tight right angle bend at the point it passes over the optic drive. The cable flexes at this point and eventually one of the copper tracks breaks. I found that if I flexed the cable at this point the track would make and break contact.

On later versions of the MacBook Pro Apple modified the HDD mount so it would prevent the case from pressing on the HDD cable. They also introduced an upgraded cable 821-2049-A, which replaced the original 821-1480-A. Unfortunately, upgraded cable still eventually breaks. This time I have taped the cable to the optic drive to try and prevent it flexing. Time will tell if this helps. The cables are quite easy to replace and I keep a few in stock.

One way of partially checking the problem is to externally connect the HDD (e.g. use a dock or SATA to USB cable) and see if the MacBook boots correctly. You need to hold the alt key down when starting the MacBook to be able to select the external drive.

At the beginning I couldn't believe that HDD cables were failing that often especially the Macbook Pro 13" A1278 2012 with cable model 821-1480-A which I have had to replace a few in the past year. Best way to diagnose this issue to me so far (after you see device passing all components tests fine and you still don't have a clue where the grief is coming from) is pulling out the hard drive and let it boot from an external usb adapter. If it boot just fine, consider replacing the hard drive cable.

Sergio- wrote:

At the beginning I couldn't believe that HDD cables were failing that often especially the Macbook Pro 13" A1278 2012 with cable model 821-1480-A which I have had to replace a few in the past year. Best way to diagnose this issue to me so far (after you see device passing all components tests fine and you still don't have a clue where the grief is coming from) is pulling out the hard drive and let it boot from an external usb adapter. If it boot just fine, consider replacing the hard drive cable.

I'm not normally one to criticize Apple for its basic designs, but this is one that seemed to be far more about form than function. This section of the Unibody MacBook Pro was not cramped for space (a 15mm drive could fit in there), and the average user never even sees the cable. A more robust (and less expensive) ribbon cable design could have saved a lot of aggravation. I do understand that it was mostly to get it down to that tiny little boxed shaped connector that goes on the main board, but if anyone could have made it work it would be Apple.

I'm wondering why some enterprising company hasn't produced an aftermarket replacement cable/connector, unless Apple has a patent on the connector to the logic board.

l008com wrote:

So I got to thinking. Computers with bad cables don't crash, or freeze. They just hang for a while randomly, then come back. JUST like a hard drive with lots of bad blocks. So what could be causing this?

Internal cables are actually not cables but flexible circuit boards, usually mylar, with printed circuit traces taking the place of wires. This type of cable can experience cracks in traces due to aging, heat, vibration, impact and abrasion. They can be damaged quite easily if the unit is mishandled during assembly or re-assembly.

In the case of an intermittent generic failure, the electrical continuity of a cracked trace on both sides of the crack is very often a function of the temperature of the unit at the point where the crack exists. As a unit heats up, it expands, and as it expands, the crack widens, eventually forcing a complete electrical separation to exist on both sides of the crack, hence a failure. As it cools down, electrical contact may once again be restored.

Addendum—I see now this thread is almost a year old. If the HDD/SSD is removable it has always been the go to way to diagnose by putting it in an external enclosure bypassing the internal SATA cable. Nothing new here.

I just had one of these faults and thought I'd add the symptoms here to help others. I had an SSD in the Mid-2012 MacBook Pro hard drive slot, and all of a sudden, it's speed dropped dramatically from 400MBytes/second to 5MBytes/second. Removing it and putting it in a USB3 external housing restored the speed. You guessed it - replacing the drive cable (again) restored the full speed. Now I've bought a few more cables to have in stock, ready for the next time.

@leroydouglas Thanks you for the interesting comment on the thermal effects on the HDD cables.

I came across this old thread when I was looking to see if anyone had found a way of improving the life of the these cable. Given that the thread comes up high in a Google search and that it has had some quite recent traffic I thought it may be help to someone if I added my experience to it.

I agree that the use of an enclose to test the HDD is old news and the only reason for mentioning it was 1008com that had recently added a comment to the thread suggesting there was no definitive way to diagnose a problem with HDD cables. My view is that if the HDD works in the enclosure but not in the MacBook it makes trying a new cable worthwhile.

You were looking for a way to diagnose. Put a stripe of tape down, and if the problems is cured, replace the cable as a permanent fix (but maybe leave the tape). This could be much more satisfying than "replaced cable and came clean".

If Brue computing is correct, the mechanism is explained by abrasion, and answers why these Macs and not every device that uses similar flex cables.

There is a close up of an abraded cable in his Video as well.

valenja wrote:

I would not trade my macbook pro 2012 for any newer model. With Mac OS High Sierra my computer is still running smooth and quick.

I'm interested in learning if the "red tape fix" has this any long term effects?

Yes the long term effect should be the cable is not susceptible to abrasion.

I have a 2012 and I have had no issue with the SATA cable to this day.

(MacBook Pro (15-inch Mid 2012), macOS (10.13.2), i7 480GB SSD 16GB RAM)

I can add—Internal SATA cable are actually not cables but flexible circuit boards, typically mylar, with printed circuit traces taking the place of wires. This type of cable can experience cracks in traces due to aging, heat, vibration, impact and abrasion. They can be damaged quite easily if the unit is mishandled during assembly or re-assembly.

In the case of an intermittent generic failure, the electrical continuity of a cracked trace on both sides of the crack is very often a function of the temperature of the unit at the point where the crack exists. As a unit heats up, it expands, and as it expands, the crack widens, eventually forcing a complete electrical separation to exist on both sides of the crack, hence a failure. As it cools down, electrical contact may once again be restored.

If the HDD/SSD is removable it has always been the go to way to diagnose by putting the drive in an external enclosure bypassing the internal SATA cable. Nothing new here.

One of many reasons Apple went to the PCI-e and soldered storage.

I think you're absolutely right about a failing hard drive cable making intermittent I/O errors at some proportion.

Unfortunately the only diagnostic tool I can think of requires the laptop to be booted and can be displayed in the console app.

I recently diagnosed a failing cable that caused a computer to run slowly. The console app showed a cascade of of I/O failures during periods of the cable failing. It might be a good thing to check.

Hello.

Original disk is only SATAI/SATAII.

Controller on board supports also SATAIII

If you put inside new SSD disk in order to get better performance, or solve bad drive issue, it can lead to worse situation. Because new drive will negotiate SATAIII with controller, and this higher communication speed od SATA bus and on bad flex cable cause this situation. It looks like bad new SSD drive, but isn't. It's still only bad flex cable problem.

It might be worth checking if the cable is shorting to the case. The inside surface of the case of some earlier MacBooks had a slightly rough surface which could wear through the cable's insulation. This problem is mentioned earlier in this thread.

that looks like it has the right firmware upgrade already, so that is not likely to be the problem. false alarm.

The first new cable could be the problem. Some users found their original cables supported their old drive (which transferred data more slowly) but failed with the newest, fastest SSD drives. so perhaps the increased speed of your new SSD drive is causing the failure to show up.

If you have a new cable coming, what happens with that newest cable will be interesting.

The SSD should work in the bay. I put a Crucial (MX200 SSD) 1TByte SSD in mine without any problems. The only thing I can think of is that the connector which plugs into the SSD is not connecting properly. It only takes a small tolerance error to get a bad connection. It would be worth looking at both the SSD and MacBook connectors with a loupe. The connector is divided into two parts (7 pins and 15 pins) and I think only the 7pin part of the connectors is used.

I would also suggest you get a spare cable. Chances are you will need it at some stage. What happens is that the MacBook case flexes slightly and pushes the cable and eventually one of the tracks breaks. I have used both types

821-1480-A

821-2049-A

but I would recommend the 821-2049-A.

BTW I understand that both the HDD and optic drive bays are SATA III. Some people have installed their SSD in place of the optic drive.

Hi,

Do you ever notice any physical wear on the cable? One youtube "fix" I saw involved simply insulating the cable with a piece of tape from the MBP's case where it had actually scraped a tiny portion of the very thin insulation off.

I have replaced several of these cables and they all broke at right angle bend just near the two screws that clamp the cable to the case. If the cable is working with the HDD then it is unlikely to be a cable fault. However, I have found that some new cable only last a short time and they can intermittently reconnect.

It would be interesting know what happens if you reboot while holding option (alt) down. If the SSD is connected properly it should appear as a bootable drives.