MacOSG: Shortcut to resetting SMC on MacBook Pro (Late 2008 and later)
Over time, the settings in the System Management Controller may become unusable, which can result in operational anomalies with the computer. Examples include not turning on, not waking from sleep, not charging the battery, or not recognizing the AC Adapter, among others.
Resetting the SMC is not intended for resolution of a stall or situation in which the computer is unresponsive. An SMC reset should not be necessary except as a last resort in cases where a hardware issue with the power management system is suspected. Performing an SMC reset resets the hardware power management functions.
On the MacBook (13 inch, Late 2008), MacBook Pro (15-inch, Early 2008), and MacBook Pro (17-inch, Early 2008) laptops, use the following steps to reset your SMU.
1. If the computer is on, turn it off.
2. Disconnect the AC adapter and remove the computer's battery.
3. Press and hold the power button for 5 seconds and then release the button.
4. Reconnect the battery and AC Adapter.
5. Press the power button to restart the computer
Just like the MacBook Air, there is no need to pull the battery out of the MacBook Pro (Late 2008 and later. Simply use the following key combinations to reset your SMC.
1. If the computer is on, turn it off by choosing Shutdown from the Apple () menu.
2. Connect the power adapter to a working power source.
3. On the built-in keyboard, press (left) Shift-Control-Option along with the power button once.
4. Wait 5 seconds and press the power button to start the computer.
[Source: Apple Technical Articles]