Problem Apple Hardware Test

At least one (or perhaps both) of your internal hard drive cables is defective as evidenced by the iCRC and UDMA CRC errors. In addition the hard drive does not have much more life left in it since the Load Cycle Count is getting dangerously near its maximum lifetime count and should be replaced very soon. It is likely the source of the problem.

Just because you installed another used SATA cable does not mean that cable is any good either. Keep in mind that Apple would replace these SATA cables pro-actively even if the laptop did not show any symptoms which is the only time I can ever recall that Apple proactively replaced anything that was failing.

You really should replace both the SATA Cable and replace the worn out hard drive with an SSD since SSDs are inexpensive and the performance improvement will be significant. A Crucial MX500 250GB SSD is at most $50 (a 500GB is about $65), but stay away from the BX500 series as they are a budget economy model that can be as slow as a hard drive under certain conditions.

Edit: I should add that not all of the SATA cable failures show up as iCRC or UDMA CRC errors and the symptoms of a bad cable vary greatly.

Create a Knoppix Linux USB boot disk using Etcher (Mac/Windows/Linux). Use Knoppix version 8.2 since the latest version 8.6 is a bit glitchy with the video. Option Boot the Knoppix USB drive and select the orange icon labeled "EFI". It may appear the computer is frozen on the Apple boot picker menu while Knoppix boots so give Knoppix lots of time to finish booting.

At the Knoppix desktop click on the "Start" menu in the lower left of the Taskbar and navigate to "System Tools --> GSmartControl". Within the GSmartControl app double-click on the laptop's drive icon to open up the drive's health report. Post the complete report here.

Hi,

You'd better make Genius Bar reservation or take your MacBook Pro to Apple Authorized Service Provider to be examined it.

From >System Information> you can see your if you hardware is 3G (SATA ll) or 6G (SATA lll)

ref: https://discussions.apple.com/thread/4478910

acidburn87 wrote:

I have a problem, every now and then this macbook pro 13 "2012, does not see the hard disk and the folder screen appears with question mark, I tried to replace the hard disk and also tried the flex hdd, every now and then it works and sometimes not ,

Did you replace the SATA cable? This is a known issue with the 2012

https://eshop.macsales.com/item/Apple/8211480/%20%2013%22%20MacBook%20Pro%20SATA

Booting from an external clone will bypass both the internal HDD/SSD and SATA cable as a test.

Boot clone https://discussions.apple.com/docs/DOC-10081

acidburn87 wrote:

I have no data problem, the first hard disk is damaged and does not read anything, but this is not a problem, from external USB it works but obviously it is slower and ugly to use,

with 20 € I found a caddy to put it in instead of the DVD that I don't use, could it be a valid solution?

I don't quite grok the problem, replace the bad drive; if you want a second drive put one in the DVD caddy.

You say " I tried to replace the hard disk and also tried the flex hdd, every now and then it works and sometimes not "

It is quite possible you do have a bad SATA cable even new out of the box—

Internal SATA 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 or  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.