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Modèle A1278 mi-2010 / processeur core 2 Duo à 2.4 ou 2.66 GHz

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Mac freezes constantly - get error code: 4SNS/1/40000001:TN1D--1.000

For about a week ago my MacBook Pro first started doing it, it began freezing very often and there was nothing to do other than rebooting it. So I decided to do a clean install of Snow Leopard, because maybe that would work, so I started my Mac from the Snow Leopard install disk, partioned my harddrive and installed Snow Leopard, I then rebooted. This didn't solve anything, so I did a Apple Hardware Test. It gave me the following error code: 4SNS/1/40000001

As it is now, I have no warranty, and as the repair services here are very expensive, it would be really nice if this was something I could fix myself.

By googleing the error code, it seems to be some sort of heat sensor, but more I really don't know.

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Hi Mattias,

I was getting the exact same error message about a year ago. My mbp was brand new when I started to get all those freezes. I also noticed that airport would drop the connection or was really slow. This started happening when I just got my band new mbp. Obviously it was still under warranty and they replaced the logic board which solved both the freezing and the wireless issues. I don't think I've seen a freeze after that.



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The SNS indicates it is a temperature sensor. There are a number of them on the board. To try to figure out where the problem sensor is I suggest you start by downloading and installing iStat, it is a free program, to monitor the various temperatures on your laptop and the fan RPMs. Here is a link to where you can download it from and read about it. The next thing I suggest you do is go through your system log to see what the operating system says is going on when it freezes. Here is a link telling you how to get to your system log file.

Since it is freezing I would say the problematic heat sensor has something to do with either the CPU or Video chip. After you have acquired a temperature profile from the various sensors. You may want to download and install smcFanControl, another free program, you can download it from here. That may stop it from freezing since you will have some control over the fan speed. But turning up the fan speed is noisy and it doesn't solve the root of the problem. I suggest you change out and apply new thermal compound to the CPU and Video chip, also clean your heatsink and fan to help prevent permanent damage to those chips. This may even solve your problem. If you decide to do this I suggest you use Arctic Silver thermal compound. You can find that here. The instructions for replacing the heatsink will guide you through the process of getting to the heatsink and fan. You can find that here.

Has your fan been running abnormally high or not at all? Please tell us about the fan operation. Please inform us of the various temperatures and fan rpms iStat is reporting. Also what country are you in?

Image Arctic Silver Thermal Paste


Arctic Silver Thermal Paste


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My fan has just been running normally, not high at all.

Under iStat I get the following temperatures and fan rpms:


HD macintosh - 31

Cpu - 48

Enclosure base - 30

Enclosure base 2 - 30

Enclosure base 3 - 28

Heatsink B - 42

Northbridge - 38


Exhaust - 1994 rpm

And I'm in Denmark.


Thank you for your reply. Those temperatures don't sound bad and the fan is just idling. Have you been using the laptop? Please keep monitoring the temps. Have you reset the SMC since you reloaded Snow Leopard? If not reset the SMC now. Here are instructions for that: _______ I have been doing some research on this. The TN of the "TN1D" in the error code stands for Temperature Northbridge. I have not been able to figure out the 1D yet, it should be something(s) giving better definition to the error. Your Northbridge is your video chip. With that knowledge and the laptop freezing, I suggest you change out and apply new thermal compound to the CPU and Video chip, also clean your heatsink and fan as I previously mentioned.


Thanks for your help, I really appreciate it!

I have been using my Mac a bit today, but I've noticed another problem. The AirPort often seems to stop working, and then when I reboot it works fine again. Can this be related to the problem I have with the heat sensor?

But I noticed that the temperatures went up at some point. Safari was working really slow, even though it was the only application I had opened. I don't know if it's any help, but here are the temps:


HD: Macintosh - 31

CPU - 72

Enclosure base - 30

Enclosure base 2 - 30

Enclosure base 3 - 29

Heatsink B - 57

Northbridge - 42


Exhaust - 318


Also, I took this out of the console, right after my Mac froze:

23/09/11 09.34.24[73] ([94]) Exited with exit code: 1

23/09/11 09.34.37[52] Fri Sep 23 09:34:37 Ms-MacBook-Pro.local WindowServer[52] <Error>: kCGErrorFailure: Set a breakpoint @ CGErrorBreakpoint() to catch errors as they are logged.

23/09/11 09.35.17[130] Debugger() was called!

23/09/11 09.36.56[1] launchd[1] has started up.

23/09/11 09.37.22[76] ( Falling back to default Mach exception handler. Could not find:

23/09/11 09.37.24[76] ([96]) Exited with exit code: 1

I will look into change out my thermal compound. I haven't really been opening a mac ever before, so do you think this can be accomplished by someone totally new to this?


I do not like your last CPU temperature. I believe if you go about the procedure methodically, take notes with drawings and closely follow the guide, you will do fine. I would like to add one more guide since you have never applied thermal paste/compound. It should be applied as thin as you can and still cover. Comment appliquer de la pâte thermique I personally have always use part of a match book or credit card to spread the thermal compound out thin and evenly.


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Hi there, got the same trouble with my mac mini mid 2010. Since it was out of warranty already, I took it to a repair place, but the technician said the computer was running cold, and he could not determine what the trouble was. the easy fix was to exchange the main board, but too expensive for me. Then an apple solution consultant Luis Sanchez @ the local Bestbuy in Secaucus, NJ told me to get the computer to the apple store. I took it to the the store in Paramus, NJ and without warranty they took care of the problem. They did replace the main board and the memory too. No charge. That is what I call good service. Maybe you want to try it.

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Hi, there. I have this same error message (with a white macbook unibody from dec 2010), and yes, the fan is running at 6200rpm. Very loud noise. So I guess the temperature sensor for the fan is not working, and giving wrong info to the fan. Very annoying...

Any idea if this specific temperature sensor could be replaced on it's own (without changing the whole motherboard)?



and recently airport started to switch off at random times also, so indeed, the same symptoms as here above...

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Mattias Damsgaard sera éternellement reconnaissant.
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