PowerBook G4 15": trackpad area overheating, resulting in sudden sleep

An issue where the internal trackpad temperature measurement is (perhaps erroneously) inordinately high, triggering a sudden system invocation of sleep appears to affect some later PowerBook G4 15" models.

Units experiencing this issue will often display the following error message in their system log (you can view the system log using the Console, located in /Applications/Utilities):

Nov 13 12:36:04 localhost kernel: Power Management received emergency overtemp signal. Going to sleep.

A poster to the MacFixIt forums writes:

"My PB G4 1.67GHz OS 10.3.9 is incorrectly registering incredibly high temperatures in the trackpad (I checked this with 'temperature monitor' - anywhere from 140-250 degrees celsius, which, if correct, my fingertips would be serious toast) This false sensor information is causing an emergency overtemp signal to be sent to my Power Management thereby putting the computer suddenly into sleep mode. This problem is inconsistent but chronic."

Potential workarounds

Disable temperature sensors You can disable the temperature sensors implicated in this problem by navigating to /System/Libraries/Extensions  and removing the following items (Do not delete them; move them to a different location in case you decide to restore the sensors later):

• IOI2CControllerPMU.kext
• IOI2CLM7x.kext
• AppleLM7x.kext
• Extensions.kextcache
• Extensions.mkext

then restarting

This procedure may void your Apple warranty, however, and could prove dangerous should an actual temperature runaway event occur. The automatic sleep mechanism is designed to prevent components from suffering physical heat damage.

Remove battery when connected to power Some users have been able to sidestep this issue by removing their batteries while units are connected to external power. 

Feedback? Late-breakers@macfixit.com.

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