S.M.A.R.T. error > New hard drive gives flashing question mark

I've read around on the site, and I THINK this is what I need to do. Would love if someone could confirm so I can go ahead and buy the parts without them going to waste!


  1. My iMac broke down on me.
  2. When I start it up, I get a blinking folder with a question mark.
  3. If I wait about 5 minutes, it loads to recovery mode, and it says my internal Seagate 1TB HDD has a S.M.A.R.T. error (which I now know means the drive is breaking down).
  4. I bought a new WD HDD, replaced it with instructions from ifixit.com (ignoring the thermal sensor plug because there's no slot for it on the new HDD).
  5. When I start up the iMac again, I simply get a flashing folder with a question mark on it. I can't get into recovery mode or do anything else.

My Understanding

From reading a lot of the Q&A on this site, it seems like:


  1. Is my main problem simply that my new drive does not support SATA II? Is that why I can't get past the flashing question mark folder nor get into recovery mode?
  2. Does NOT having the sensor cable affect the iMac from starting up? Or does it only cause the fan to rotate at full speed all the time?

Thank you!

Answered! View the answer I have this problem too

Is this a good question?

Score 0


Add a comment

1 Answer

Chosen Solution

Yes, you do need to use the correct drive for your system!

In this case your system has a SATA II (3.0 Gb/s) HD port so either a fixed SATA I (1.5 Gb/s) or SATA II (3.0 Gb/s) drive will work. Today, there are a few auto sense drives with sense the systems SATA I/O speed and will match it as well.

Western Digital no longer offers any SATA II drives in their current drive line up. So you will either need to find an older WD drive or will need to check out a different companies offering.

The other issue is the physical size of your current HD in the system is 3.5" not 2.5" so that also limits which drive you can use.

As you pointed to a SSHD drive here is the best option: Seagate Desktop SSHD and here is the spec sheet for this series: Seagate Desktop SSHD specs. Here we can see the drive has auto SATA port sense technology so it will work in your system.

As for the needed thermal sensor, Yes! It is also required. And yes, you found the correct sensor OWC offers for your system.

Directly answering your pointed questions:

1 - Yes, you do need the correct drive for the system to run recovery services as it won't tolerate errors which you will get with the SATA speed mismatch.

But, you have a bigger issue here as your system does not offer internet recovery! (review this Apple T/N: Computers that can be upgraded to use OS X Internet Recovery) and since the drive is fresh it won't have the onboard hidden recovery partition either (review this Apple T/N: About OS X Recovery).

So you'll need to either have already created an external bootable drive to boot your system or find your original grey CD/DVD OS install disk or a retail version of the OS to use to boot your system. Or, if you have access to a second Mac system you could create a bootable USB thumb drive (16 GB) and then copy to it the OS installer (or external FireWire drive) to install the OS onto your new drive.

2 - The lack of the sensor will only effect the SMC services which manages the cooling of your system not the use of the system. I don't recommend you run your system in this state as you'll likely burn out the fan and I don't recommend using software over-rides as we have learned (the hard way) it will also over time kill your system.

So the bottom line here is get a SATA II (3.0 Gb/s) 3.5" drive and the needed thermal sensor. And while that is on its way to you get a USB thumb drive and visit a friend who has a Mac with a bottle of wine or some cans of beer so you can prep up a bootable Thumb drive with a copy of the OS installer so you can fix your system. ;-}

Was this answer helpful?

Score 3



Thank you so much for the amazingly detailed answer! I recognize your profile icon from other posts of yours that I read and I learned a lot from you! Thank you!

I feel much more confident moving forward now! I'm going to follow your advice and just finished ordering the cable and sshd!

I'll post my result here about how it goes once everything's arrived and I've given it a shot!


I'd love to get you some cans of beer, too!


If you have changed the brand of the hard drive you will need the proper temp sensor cable. They are

Apple Part#

Hitachi 922-9223

Seagate 922-9224

Western Digital 922-9225


Add a comment

Add your answer

Raiman Au will be eternally grateful.
View Statistics:

Past 24 Hours: 0

Past 7 Days: 7

Past 30 Days: 21

All Time: 338