MacBook Pro mid-2012 Very slow. Kernel_task is using 300%+ CPU

A Troubleshooting Protocol to Identify Problems or Fix macOS El Capitan or Later

You should try each, one at a time, then test to see if the problem is fixed before going on to the next.

Be sure to backup your files before proceeding if possible.

1. Shutdown the computer, wait 30 seconds, restart the computer.
2. Disconnect all third-party peripherals and remove any support software like drivers and plug-ins.
3. Resetting your Mac’s PRAM and NVRAM
4. Reset the System Management Controller (SMC)
5. Start the computer in Safe Mode, then restart normally. This is slower than a standard startup.
6. Repair the disk by booting from the Recovery HD. Immediately after the chime hold down the Command and R keys until the Utility Menu appears. Choose Disk Utility and click on the Continue button. Select the indented (usually, Macintosh HD) volume entry from the side list. Click on the First Aid button in the toolbar. Wait for the Done button to appear. Quit Disk Utility and return to the Utility Menu. Restart the computer from the Apple Menu.
7. Create a New User Account Open Users & Groups preferences. Click on the lock icon and enter your Admin password when prompted. On the left under Current User click on the Add [+] button under Login Options. Setup a new Admin user account. Upon completion log out of your current account then log into the new account. If your problems cease, then consider switching to the new account and transferring your files to it - Transferring files from one User Account to another.
8. Download and install the OS X El Capitan 10.11.6 Combo Update or 10.12.6 Combo Update or Download macOS High Sierra 10.13.3 Combo Update as needed.
9. Reinstall OS X by booting from the Recovery HD using the Command and R keys. When the Utility Menu appears select Reinstall OS X then click on the Continue button.
10. Erase and Install OS X Restart the computer. Immediately after the chime hold down the Command and R keys until the Apple logo appears. When the Utility Menu appears:

1. Select Disk Utility from the Utility Menu and click on Continue button.
2. When Disk Utility loads select the drive (out-dented entry) from the Device list.
3. Click on the Erase icon in Disk Utility's toolbar. A panel will drop down.
4. Set the Format type to APFS (for SSDs only) or Mac OS Extended (Journaled.)
5. Click on the Apply button, then wait for the Done button to activate and click on it.
6. Quit Disk Utility and return to the Utility Menu.
7. Select Reinstall OS X and click on the Continue button.

maestroscherzo wrote:

There is nothing at all installed on the Mac, so I can only assume it’s some sort of hardware issue.

That is correct. A defective hard disk drive cable is certainly among the possible causes.

Please readIf kernel_task is using a large percentage of your Mac CPU - Apple Support as well as the links within it.

A runaway kernel_task can be due to a number of factors, such as:

• a failed or disconnected temperature sensor
• cooling system inefficiency (an inoperative exhaust fan on Macs so equipped, possibly clogged with dust, including the heat sink)
• a worn out, missing, or non-Apple (user-installed) battery on portable Macs
• similar hardware-specific causes including internal hardware additions or modifications, external USB and other connected devices, or the driver software required to use them.

Each of those possible causes is equally important and requires its own investigation.

If you can find no other explanation for its behavior, an SMC Reset is justified: Reset the System Management Controller (SMC) on your Mac - Apple Support.

If all else fails Contact Support.

As for having only Apple techs work on it, that would be great.

It would be, but they will absolutely, positively refuse to service a Mac that has had user-installed modifications. However, they will provide a diagnosis, perhaps at no charge. I strongly suspect they will conclude liquid damage. I also suspect the seller attempted to conceal that damage.

If so the repair will require replacement of practically every major component with the possible exception of the display assembly. It is not limited to the logic board. It will not be economically justified. If you want to fix it, the best option for repairing it yourself will be to source replacement parts from reputable vendors. Working on that model is microsurgery that even I do not perform on anyone else's Mac, unless they already wrote it off as a total loss.

I agree with Mr. etresoft's conclusions and recommendations: cut your losses... unless of course you are interested in repairing your Mac strictly for the learning experience, which will certainly be valuable.

If you need an operational Mac and want to save a few bucks, purchase a Mac from Apple's Refurbished and Clearance page. They are indistinguishable from new and carry the identical warranty and AppleCare eligibility as brand new ones. They just cost a lot less.

Just like repairing one, purchasing a used Mac is best left for very experienced Mac users. A good Mac in serviceable condition offered by a reputable seller who properly prepares it for sale (conditions that are very rarely met) fetches nearly as much as Apple charges for a refurbished one anyway.

Hello maestroscherzo,

Can you explain in more detail exactly what hardware modifications you have done, or paid someone else do to?

Replacing the hard drive in one of these machines is just about the easiest thing you can do. There is absolutely NO reason to unplug the fan or any other component other than the hard drive. The components on the motherboard are extremely small and delicate.

Unfortunately, it sounds like your machine may have been irreparably damaged. Was this shop an authorized Apple Repair Centre? Apple, or an authorized Apple Repair Centre may be able to test the machine and repair it. But if they have to replace the motherboard, it won't be cheap.

Now I’m starting to think that the Mac must think it’s severly overheating.

That's exactly what causes the runaway kernel_task. If they are going to be performed, hardware repairs or modifications must absolutely, positively be performed by knowledgeable Mac experts, and from what you describe sadly that wasn't the case.

Macs have many thermal sensors and all of them must be present and 100% operational. If they are not, its systems will default to a self-protection mode that includes throttling the CPU to intentionally limit its performance. At an extreme kernel_task will prevent it from doing much of anything else.

The solution is to fix defective hardware and use a SSD obtained from a manufacturer that unequivocally supports Macs. Many commonly available SSDs just don't work well, if at all, or may stop working upon some minor firmware update in the future.

If returning that Mac for a refund is an option, do it. As you wrote it's been slow since you got it. Given operational hardware no Mac should ever be slow.

John Galt explained it very well. The fan running full blast is another symptom of this self protection mode.

If you are handy with such things, you could disassemble the machine using one of the many tear-down guides posted on the internet. Identify each port that should be connected and make sure it is.

However, this is very delicate. I replaced the keyboard on just such a machine about a month ago. Even my reading glasses weren't good enough for me to see the connector. I had to use my iPhone's super-zoom mode. Also, I had the OWC kit with all the right torx drivers and semisoft plastic spudgers.

It is very likely that one of those connectors is already broken. If so, you won't be able to fix it. When you reassemble it, the machine probably will not run at all anymore.

I still don't know the full history of this machine. Perhaps some previous owner had irreparably damaged the motherboard and unplugged the fan just to keep it quiet. Then they sold it to you to make it your problem instead.

I suggest you bit the bullet, cut your losses, and get a new machine.

maestroscherzo wrote:

The code the hardware test gave is

4SNS/1/C0000008: TsOP—124

A bit of research is saying that it is the palm rest temp sensor. Any ideas where abouts that is? Thanks.

I understand it's integrated into the trackpad. Apparently previous liquid spills can damage the sensor.

http://www.powerbookmedic.com/MacBook-Pro-13-Unibody-Trackpad-p-17444.html

etresoft wrote:

Replacing the hard drive in one of these machines is just about the easiest thing you can do. There is absolutely NO reason to unplug the fan or any other component other than the hard drive. The components on the motherboard are extremely small and delicate.

Some recommendations seem to be to pull the battery connector for anything done under the hood.

The OP seems to think it’s limited to the trackpad, which is a lot easier of a DIY job than anything that requires removing the logic board. I think you might be overstating the difficulty in buying a used Mac. I would have asked to see it run AHT though. A used mid-2012 might sell for $400 and I think is a very good value.

maestroscherzo wrote:

In regards to the difficulty of the tasks, at this point, I am pretty much willing to try anything. Having already disassembled the whole machine, including taking out and reinstalling the logic board, I know I could switch out the trackpad in about 20 minutes. The new trackpad should arrive tomorrow and I am hoping that it solves this problem. At this point, as the AHT is not indicating any additional/other errors, I am a bit more confident in this than my other attempts thus far.

As for the value, I purchased this one at a steal of a deal, and I knew that I may be encountering a problem or two. In my area, used these models of MacBooks are rarely seen for sale under $500.00, so in terms of value, even now I am still quite under that total.

Although I may disagree that I should cut my losses and/or not work on it myself, I do appreciate you all taking the time to reply and give me some ideas on where to go with this. I feel like I'm actually getting somewhere with it now. I will update and let you know how it goes once I install the new trackpad after it arrives. Thanks again!

I personally find the 13" mid-2012 MBP (which I bought new in 2015) to be one of the more desirable models because it's easier to tinker with. The new ones are cool and everything, but there's something to be said for easy to replace memory and drive, along with the optical drive and multiple connections. The new machines don't even perform that much better because there really hasn't been that much of an advance in processor technology. There are also a lot of them with the last one sold new in 2016, so Apple will still have hardware support even though they might not help you out if you've taken apart more than just the drive and memory. There are also a lot of them out there, so salvage parts should be easy to come by for a while.

I personally would feel uncomfortably taking apart the logic board, but a trackpad replacement seems relatively straightforward. Let us know how it turns out.