PowerOn Self Test POST Error Codes

The computer automatically performs a power-on self test when it is turned on after being fully shut down not a restart . This section describes what to do if you hear beeps during startup. When this occurs, the sleep LED will stay on, occasionally flashing. MacBook Pro relies on a combination of tones and blinking sleep LEDs to display power-on self test POST error codes. If the computer detects no SDRAM Synchronous Dynamic Random Access Memory also referred to as RAM , or the RAM installed...