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 indicator light stays on, occasionally flashing.

MacBook Air relies on a combination of tones and blinking sleep indicator light flashes to display power-on self test (POST) error codes.

If the logic board has a RAM chip issue, the screen remains black and the LED blinks once per second to signal the error.

If the MacBook Air's diagnostic LED displays five flashes upon startup, and the pattern repeats after a brief pause, the computer's battery may require service. If the power adapter is present and connected to a working power source, the MacBook Air will continue to start up normally despite a defective battery.

This 5-flash LED diagnostic may also occur when waking the computer from sleep if the power adapter is connected and the battery requires service. This informs the customer that the battery requires service while accommodating continued operation until it can be diagnosed.

Related Knowledge Base articles:

303363: Intel-based Mac: Startup sequence and error codes, symbols 307284: MacBook Air: About the Diagnostic LEDs

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  • dehab
    How to test macbook power adapter?
    9 years ago

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