2012 MacBook Pro 9,2 - Sometimes boots, sometimes beeps loudly 3 times and refuses to boot, and sleep light usually flashes 5 times

[izzy0242mr]

I have a 2012 MacBook Pro (9,2). It's had a weird range of issues and I haven't been able to narrow it down yet:

• When initially booting, the computer's sleep light flashed 5 times, then does the loud error beep 3 times in a row on repeat. (8 GB RAM total, both slots full)
• I swapped out the RAM, no change (both slots full, 4 GB RAM total)
• I unplugged the battery, then was able to boot into recovery and reinstall macOS.
• However, when I slightly jostled the computer (with the bottom panel off) the screen would glitch and it would freeze. Had to restart to fix it. Happened a bunch of times so I finally stopped jostling it.
• Booted up successfully. Used it for a bit, no issues.
• Plugged battery back in, was able to boot up again, no issues (though macOS said battery needs replacing)
• Put one stick of the original RAM into one slot, left the other empty. Booted but took a really long time. (4 GB total, only one slot full)
• Then forced reboot and tried to boot up again, but I'm back to the 3 error beeps + 5 flashing lights.

Weird thing is that the computer will SOMETIMES show the 5 flashing lights before trying to boot (more often than not), but not always. And even when it does show the 5 flashing lights, sometimes it will boot all the way up, and sometimes it will do the 3 loud error beeps.

The inconsistency is what's confusing me. It's not bad RAM—all my RAM sticks have booted the Mac at least once. It's not the battery—computer has booted with and without the battery plugged in (battery is bad, yes, but that doesn't seem to be the issue).

My theory is that something is wrong with one of the RAM slots and that jostling the laptop with the RAM in said slot might have caused a kernel panic, but I am not sure why it wouldn't boot with that slot empty.

 

[Fishrrman]

The "three beeps" is usually "RAM related".

However...
The 2012 unibody MacBook Pros are notorious for failing drive ribbon cables.

When the cable starts going bad, the Mac will have problems booting/running, because "communications" between the drive and motherboard can get erratic.

The cable is cheap and easily changed out.
You can get the part number from ifixit.com.
You can either buy it from them or from elsewhere online.

I suggest you swap out the ribbon cable, and then see how things go from there.

Save this thread and get back to us with your results.

Good luck.

 

[izzy0242mr]

The "three beeps" is usually "RAM related".

However...
The 2012 unibody MacBook Pros are notorious for failing drive ribbon cables.

When the cable starts going bad, the Mac will have problems booting/running, because "communications" between the drive and motherboard can get erratic.

The cable is cheap and easily changed out.
You can get the part number from ifixit.com.
You can either buy it from them or from elsewhere online.

I suggest you swap out the ribbon cable, and then see how things go from there.

Save this thread and get back to us with your results.

Good luck.

Thanks. Haven't tried this yet - but I realized I hadn't actually vigorously tested one specific RAM slot as much. I left the bottom (if the Mac is upside down for disassembly) slot empty while the top slot has a stick in it. So far I haven't had the beeping, the 5 flashes very often, or any issues booting.

I'm going to keep using/testing and if the problem happens again I may look into the hard drive cable. Wouldn't have expected that so I appreciate the tip.