Interpreting POST diagnostic front panel LEDs and audible codes
This section covers the front panel LED codes as well as the audible codes that may occur before or during
POST that do not necessarily have an error code or text message associated with them.
WARNING! When the computer is plugged into an AC power source, voltage is always applied to the system
board. To reduce the risk of personal injury from electrical shock and/or hot surfaces, be sure to disconnect
the power cord from the wall outlet and allow the internal system components to cool before touching.
NOTE: Recommended actions in the following table are listed in the order in which they should be
performed.
Not all diagnostic lights and audible codes are available on all models.
Table 10-3 Diagnostic front panel LEDs and audible codes
Activity Beeps Possible Cause Recommended Action
White Power LED On. None Computer on. None
White Power LED ashes every
two seconds.
None Computer in Suspend to
RAM mode (some models
only) or normal Suspend
mode.
No action required. Press any key or move the mouse
to wake the computer.
Red Power LED ashes two
times, once every second,
followed by a two second pause.
Beeps stop after fth iteration
but LEDs continue until problem
is solved.
2 Processor thermal
protection activated:
A fan may be blocked or not
turning.
OR
The heat sink/fan assembly
is not properly attached to
the processor.
OR
The unit has vents blocked
or is in a location where the
ambient temperature is too
high.
1. Ensure that the computer air vents are not
blocked and the processor cooling fan is
plugged in and running, if equipped.
2. Contact an authorized reseller or service
provider.
Red Power LED ashes four
times, once every second,
followed by a two second pause.
Beeps stop after fth iteration
but LEDs continue until problem
is solved.
4 Power failure (power supply
is overloaded).
OR
The incorrect external
power supply adapter is
being used on the unit.
1. Check if a device is causing the problem by
removing ALL attached devices. Power on the
system. If the system enters the POST, then
power o and replace one device at a time and
repeat this procedure until failure occurs.
Replace the device that is causing the failure.
Continue adding devices one at a time to
ensure all devices are functioning properly.
2. Replace the power supply.
3. Replace the system board.
Red Power LED ashes ve
times, once every second,
followed by a two second pause.
Beeps stop after fth iteration
but LEDs continue until problem
is solved.
5 Pre-video memory error. CAUTION: To avoid damage to the memory
modules or the system board, you must unplug the
computer power cord before attempting to reseat,
install, or remove a memory module.
1. Reseat memory modules.
2. Replace memory modules one at a time to
isolate the faulty module.
72 Chapter 10 Diagnostics and troubleshooting
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