June 16, 2006 8:14 AM PDT

MacBook Special Report: Sudden shutdowns -- possible fixes

by CNET staff

Some MacBook (13") units suddenly shuts down in the middle of normal operation.

Usual suspects for this type of issue are corrupt PRAM, improperly seated or bad RAM, or a problematic PMU. However, users have yet to find relief from the symptom with these traditional workarounds. Diagnostics performed using the Apple Hardware Test CD have also failed to yield conclusive evidence of component failure.

Some clues point to overheating, though we certainly can't say that such is the cause in some, let alone a majority of sudden shutdown cases.

It appears that affected units have flawed logic boards, which are being replaced on a case-by-case basis.

General cases The timing of the sudden shutdowns is variable, with some users reporting the incidents soon after starting up, and others noting occurrence after long periods of processor intensive applications.

MacFixIt reader Ryan writes:

"I have a MacBook 2 GHz with 2GB of Apple DDR2 SDRAM and a 120G HD. I purchased this computer from Apple.ca and received it on May 18th. Last Friday was my first encounter with the mysterious shutdown problem. This now happens several times a day (I feel like I'm using Windows), it does not matter if the computer is cold, hot, or if I'm playing games (Civ IV) or just checking email. My RAM was Apple installed and I have checked to ensure that it is properly seated. I have zapped the PRAM and run the Apple hardware test several times. The test found nothing, even though my MacBook shutdown during my first test."

Richard Newton adds:

"Twice it has happened to mine within two minutes of waking up from several hours of sleep. The case was completely cool to the touch. I can find no pattern to this. It just ran for 3 days with multiple programs active and quit this morning while I was reading news. It has happened twice in a row with only Safari and Mail running. At least mine re-boots the first time. So far, I have had this happen 9 times in the last two weeks. The machine is 5 weeks old."

Possible software-based workaround Although the majority of sudden shutdown cases appear to be due to problematic hardware, a handful of readers are reporting success with software-based workarounds.

In particular, some users are finding success with a workaround we've suggested for various wake-from-seep and related issues -- deletion of the following files:

~/Library/Preferences/com.apple.systemuiserver.plist
/Library/Preferences/SystemConfiguration/com.apple.PowerManagement.plist

This workaround may need to be repeated from time to time as these files can become corrupt with some frequency.

Sent for repair Users are getting mixed results when sending MacBooks in for repairs. Some users are having their units' fans replaced, others are receiving a new logic board.

MacFixIt reader Simon writes:

"I experienced a similar thing in the past as form the first day I bought my MacBook but I didn't get to the problem until I installed Core Duo Temp and found that the fan was not working and when the temperature got to 78-80°C the machine unexpectedly shut down. The first move was to change the motherboard but but nothing had changed. The fan was working a little just if the machine was waked up from some hours of rest. When the machine was hot the fan stopped working. The solution was changing the fan. I also noted that the sound of the factory mounted fan was similar to a 'mooing' and the sound of the new fan is like all other computers' fans."

R. Newton adds:

"My MacBook has just been set back a second time to address the sudden shutdown issue. The logic board was replaced during the first repair, and it seemed to fix the problem. Two weeks later, the sudden shutdown problem begin to occur again. The current suspect is that the heat sensors were not calibrated, or are just bad."

Re-seat RAM The fix, in other cases, is to re-seat the RAM modules. For instructions on accessing the MacBook's RAM modules, see this Apple manual.

Try removing the RAM modules then firmly seating them back in place.

As described in Apple Knowledge Base document #303083:

"If the computer detects no SDRAM (Synchronous Dynamic Random Access Memory, also referred to as RAM) or the RAM installed does not meet the appropriate specifications, the screen will remain black but the power LED on the front of the computer will blink once per second to signal the error. This error condition may be due to physically damaged RAM, installing the incorrect type of RAM, or not having RAM installed."

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