Ask Max: Resoving A Sleep Issue Through PMU Reset
I am having trouble with the sleep feature. Recently I am not able to sleep the computer by any command means then if it sleeps from time, under system prefs. It will not wake, have to restart. Can the PMU be reset on this model? If so where is it located?
If resetting the PMU fails to resolve your problems you should then remove any added PCI cards you have installed. Some USB/Firewire cards will prevent a computer from sleeping properly. If you still have issues with your system sleeping, try removing all non-Apple RAM and peripherals, as this may interfere with the system’s ability to go into the low power mode of sleep.