Chosen Solution
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.
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?
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.
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)? edit
and recently airport started to switch off at random times also, so indeed, the same symptoms as here above…
